diff --git a/pubsublite/errors.go b/pubsublite/errors.go
new file mode 100644
index 0000000..1101188
--- /dev/null
+++ b/pubsublite/errors.go
@@ -0,0 +1,22 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+
+package pubsublite
+
+import "errors"
+
+var (
+	// ErrOverflow indicates that the publish buffers have overflowed. See
+	// comments for PublishSettings.BufferedByteLimit.
+	ErrOverflow = errors.New("pubsublite: client-side publish buffers have overflowed")
+)
diff --git a/pubsublite/settings.go b/pubsublite/settings.go
new file mode 100644
index 0000000..b1db10f
--- /dev/null
+++ b/pubsublite/settings.go
@@ -0,0 +1,103 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+
+package pubsublite
+
+import (
+	"errors"
+	"fmt"
+	"time"
+)
+
+const (
+	// MaxPublishRequestCount is the maximum number of messages that can be
+	// batched in a single publish request.
+	MaxPublishRequestCount = 1000
+
+	// MaxPublishMessageBytes is the maximum allowed serialized size of a single
+	// Pub/Sub message in bytes.
+	MaxPublishMessageBytes = 1000000
+
+	// MaxPublishRequestBytes is the maximum allowed serialized size of a single
+	// publish request (containing a batch of messages) in bytes.
+	MaxPublishRequestBytes = 3500000
+)
+
+// PublishSettings control the batching of published messages.
+type PublishSettings struct {
+	// Publish a non-empty batch after this delay has passed. Must be > 0.
+	DelayThreshold time.Duration
+
+	// Publish a batch when it has this many messages. Must be > 0. The maximum is
+	// MaxPublishRequestCount.
+	CountThreshold int
+
+	// Publish a batch when its size in bytes reaches this value. Must be > 0. The
+	// maximum is MaxPublishRequestBytes.
+	ByteThreshold int
+
+	// The maximum time that the client will attempt to establish a publish stream
+	// connection to the server. Must be > 0.
+	//
+	// The timeout is exceeded, the publisher will terminate with the last error
+	// that occurred while trying to reconnect. Note that if the timeout duration
+	// is long, ErrOverflow may occur first.
+	Timeout time.Duration
+
+	// The maximum number of bytes that the publisher will keep in memory before
+	// returning ErrOverflow. Must be > 0.
+	//
+	// Note that Pub/Sub Lite topics are provisioned a publishing throughput
+	// capacity, per partition, shared by all publisher clients. Setting a large
+	// buffer size can mitigate transient publish spikes. However, consistently
+	// attempting to publish messages at a much higher rate than the publishing
+	// throughput capacity can cause the buffers to overflow. For more
+	// information, see https://cloud.google.com/pubsub/lite/docs/topics.
+	BufferedByteLimit int
+}
+
+// DefaultPublishSettings holds the default values for PublishSettings.
+var DefaultPublishSettings = PublishSettings{
+	DelayThreshold: 10 * time.Millisecond,
+	CountThreshold: 100,
+	ByteThreshold:  1e6,
+	Timeout:        60 * time.Second,
+	// By default set to a high limit that is not likely to occur, but prevents
+	// OOM errors in clients.
+	BufferedByteLimit: 1 << 30, // 1 GiB
+}
+
+func validatePublishSettings(settings PublishSettings) error {
+	if settings.DelayThreshold <= 0 {
+		return errors.New("pubsublite: invalid publish settings. DelayThreshold duration must be > 0")
+	}
+	if settings.Timeout <= 0 {
+		return errors.New("pubsublite: invalid publish settings. Timeout duration must be > 0")
+	}
+	if settings.CountThreshold <= 0 {
+		return errors.New("pubsublite: invalid publish settings. CountThreshold must be > 0")
+	}
+	if settings.CountThreshold > MaxPublishRequestCount {
+		return fmt.Errorf("pubsublite: invalid publish settings. Maximum CountThreshold is MaxPublishRequestCount (%d)", MaxPublishRequestCount)
+	}
+	if settings.ByteThreshold <= 0 {
+		return errors.New("pubsublite: invalid publish settings. ByteThreshold must be > 0")
+	}
+	if settings.ByteThreshold > MaxPublishRequestBytes {
+		return fmt.Errorf("pubsublite: invalid publish settings. Maximum ByteThreshold is MaxPublishRequestBytes (%d)", MaxPublishRequestBytes)
+	}
+	if settings.BufferedByteLimit <= 0 {
+		return errors.New("pubsublite: invalid publish settings. BufferedByteLimit must be > 0")
+	}
+	return nil
+}
diff --git a/pubsublite/settings_test.go b/pubsublite/settings_test.go
new file mode 100644
index 0000000..6c49880
--- /dev/null
+++ b/pubsublite/settings_test.go
@@ -0,0 +1,114 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+
+package pubsublite
+
+import (
+	"testing"
+	"time"
+)
+
+func TestValidatePublishSettings(t *testing.T) {
+	for _, tc := range []struct {
+		desc string
+		// settingsFunc is passed DefaultPublishSettings
+		settingsFunc func(settings PublishSettings) PublishSettings
+		wantErr      bool
+	}{
+		{
+			desc: "valid: default",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				return DefaultPublishSettings
+			},
+			wantErr: false,
+		},
+		{
+			desc: "valid: max",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				return PublishSettings{
+					CountThreshold: MaxPublishRequestCount,
+					ByteThreshold:  MaxPublishRequestBytes,
+					// These have no max bounds, check large values.
+					DelayThreshold:    24 * time.Hour,
+					Timeout:           24 * time.Hour,
+					BufferedByteLimit: 1e10,
+				}
+			},
+			wantErr: false,
+		},
+		{
+			desc: "invalid: zero CountThreshold",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				settings.CountThreshold = 0
+				return settings
+			},
+			wantErr: true,
+		},
+		{
+			desc: "invalid: CountThreshold over MaxPublishRequestCount",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				settings.CountThreshold = MaxPublishRequestCount + 1
+				return settings
+			},
+			wantErr: true,
+		},
+		{
+			desc: "invalid: ByteThreshold over MaxPublishRequestBytes",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				settings.ByteThreshold = MaxPublishRequestBytes + 1
+				return settings
+			},
+			wantErr: true,
+		},
+		{
+			desc: "invalid: zero ByteThreshold",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				settings.ByteThreshold = 0
+				return settings
+			},
+			wantErr: true,
+		},
+		{
+			desc: "invalid: zero DelayThreshold",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				settings.DelayThreshold = time.Duration(0)
+				return settings
+			},
+			wantErr: true,
+		},
+		{
+			desc: "invalid: zero Timeout",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				settings.Timeout = time.Duration(0)
+				return settings
+			},
+			wantErr: true,
+		},
+		{
+			desc: "invalid: zero BufferedByteLimit",
+			settingsFunc: func(settings PublishSettings) PublishSettings {
+				settings.BufferedByteLimit = 0
+				return settings
+			},
+			wantErr: true,
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			settings := tc.settingsFunc(DefaultPublishSettings)
+			gotErr := validatePublishSettings(settings)
+			if (gotErr != nil) != tc.wantErr {
+				t.Errorf("validatePublishSettings(%v) = %v, want err=%v", settings, gotErr, tc.wantErr)
+			}
+		})
+	}
+}