diff --git a/openstack/client.go b/openstack/client.go
index f1e8258..6e0de06 100644
--- a/openstack/client.go
+++ b/openstack/client.go
@@ -1,18 +1,60 @@
 package openstack
 
 import (
+	"errors"
+
 	"github.com/rackspace/gophercloud"
 	identity3 "github.com/rackspace/gophercloud/openstack/identity/v3"
+	"github.com/rackspace/gophercloud/openstack/utils"
 )
 
 // Client provides access to service clients for this OpenStack cloud.
-type Client gophercloud.ProviderClient
+type Client struct {
+	gophercloud.ProviderClient
+}
+
+const (
+	v20 = "v2.0"
+	v30 = "v3.0"
+)
 
 // NewClient authenticates to an OpenStack cloud with the provided credentials.
 // It first queries the root identity endpoint to determine which versions of the identity service are supported, then chooses
 // the most recent identity service available to proceed.
 func NewClient(authOptions gophercloud.AuthOptions) (*Client, error) {
-	return nil, nil
+	versions := []*utils.Version{
+		&utils.Version{ID: v20, Priority: 20},
+		&utils.Version{ID: v30, Priority: 30},
+	}
+
+	chosen, endpoint, err := utils.ChooseVersion(authOptions.IdentityEndpoint, versions)
+	if err != nil {
+		return nil, err
+	}
+
+	client := Client{
+		ProviderClient: gophercloud.ProviderClient{
+			IdentityEndpoint: endpoint,
+			Options:          authOptions,
+		},
+	}
+
+	switch chosen.ID {
+	case v20:
+	case v30:
+		identityClient := identity3.NewClient(&client.ProviderClient)
+		token, err := identityClient.Authenticate(authOptions)
+		if err != nil {
+			return nil, err
+		}
+
+		client.ProviderClient.TokenID = token.ID
+	default:
+		// The switch must be out of sync with "versions".
+		return nil, errors.New("Wat")
+	}
+
+	return &client, nil
 }
 
 // IdentityV3 explicitly accesses the v3 identity service.