diff --git a/google/example_test.go b/google/example_test.go
index 380bd47..434a373 100644
--- a/google/example_test.go
+++ b/google/example_test.go
@@ -44,6 +44,34 @@ func Example_webServer() {
 	client.Get("...")
 }
 
+func Example_serviceAccountsJSON() {
+	// Your credentials should be obtained from the Google
+	// Developer Console (https://console.developers.google.com).
+	// Navigate to your project, then see the "Credentials" page
+	// under "APIs & Auth".
+	// To create a service account client, click "Create new Client ID",
+	// select "Service Account", and click "Create Client ID". A JSON
+	// key file will then be downloaded to your computer.
+	config, err := google.NewServiceAccountJSONConfig(
+		"/path/to/your-project-key.json",
+		"https://www.googleapis.com/auth/bigquery",
+	)
+	if err != nil {
+		log.Fatal(err)
+	}
+	// Initiate an http.Client. The following GET request will be
+	// authorized and authenticated on the behalf of
+	// your service account.
+	client := http.Client{Transport: config.NewTransport()}
+	client.Get("...")
+
+	// If you would like to impersonate a user, you can
+	// create a transport with a subject. The following GET
+	// request will be made on the behalf of user@example.com.
+	client = http.Client{Transport: config.NewTransportWithUser("user@example.com")}
+	client.Get("...")
+}
+
 func Example_serviceAccounts() {
 	// Your credentials should be obtained from the Google
 	// Developer Console (https://console.developers.google.com).
diff --git a/google/google.go b/google/google.go
index e170415..eb55f4a 100644
--- a/google/google.go
+++ b/google/google.go
@@ -15,6 +15,7 @@ package google
 
 import (
 	"encoding/json"
+	"io/ioutil"
 	"net/http"
 	"path"
 	"time"
@@ -61,6 +62,30 @@ func NewServiceAccountConfig(opts *oauth2.JWTOptions) (*oauth2.JWTConfig, error)
 	return oauth2.NewJWTConfig(opts, uriGoogleToken)
 }
 
+// NewServiceAccountJSONConfig creates a new JWT config from a
+// JSON key file downloaded from the Google Developers Console.
+// See the "Credentials" page under "APIs & Auth" for your project
+// at https://console.developers.google.com.
+func NewServiceAccountJSONConfig(filename string, scopes ...string) (*oauth2.JWTConfig, error) {
+	b, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return nil, err
+	}
+	var key struct {
+		Email      string `json:"client_email"`
+		PrivateKey string `json:"private_key"`
+	}
+	if err := json.Unmarshal(b, &key); err != nil {
+		return nil, err
+	}
+	opts := &oauth2.JWTOptions{
+		Email:      key.Email,
+		PrivateKey: []byte(key.PrivateKey),
+		Scopes:     scopes,
+	}
+	return NewServiceAccountConfig(opts)
+}
+
 // NewComputeEngineConfig creates a new config that can fetch tokens
 // from Google Compute Engine instance's metaserver. If no account is
 // provided, default is used.