diff --git a/auth.go b/auth.go
new file mode 100644
index 0000000..cbe9a13
--- /dev/null
+++ b/auth.go
@@ -0,0 +1,12 @@
+package writeas
+
+import (
+	"net/http"
+)
+
+func (c *Client) isNotLoggedIn(code int) bool {
+	if c.token == "" {
+		return false
+	}
+	return code == http.StatusUnauthorized
+}
diff --git a/post.go b/post.go
index c4d4996..922ee99 100644
--- a/post.go
+++ b/post.go
@@ -1,89 +1,119 @@
 package writeas
 
 import (
 	"fmt"
 	"net/http"
 	"time"
 )
 
 type (
 	// Post represents a published Write.as post, whether anonymous, owned by a
 	// user, or part of a collection.
 	Post struct {
-		ID          string    `json:"id"`
-		Slug        string    `json:"slug"`
-		ModifyToken string    `json:"token"`
-		Font        string    `json:"appearance"`
-		Language    *string   `json:"language"`
-		RTL         *bool     `json:"rtl"`
-		Listed      bool      `json:"listed"`
-		Created     time.Time `json:"created"`
-		Title       string    `json:"title"`
-		Content     string    `json:"body"`
-		Views       int64     `json:"views"`
-		Tags        []string  `json:"tags"`
-		Images      []string  `json:"images"`
-		OwnerName   string    `json:"owner,omitempty"`
+		ID        string    `json:"id"`
+		Slug      string    `json:"slug"`
+		Token     string    `json:"token"`
+		Font      string    `json:"appearance"`
+		Language  *string   `json:"language"`
+		RTL       *bool     `json:"rtl"`
+		Listed    bool      `json:"listed"`
+		Created   time.Time `json:"created"`
+		Title     string    `json:"title"`
+		Content   string    `json:"body"`
+		Views     int64     `json:"views"`
+		Tags      []string  `json:"tags"`
+		Images    []string  `json:"images"`
+		OwnerName string    `json:"owner,omitempty"`
 
 		Collection *Collection `json:"collection,omitempty"`
 	}
 
 	// PostParams holds values for creating or updating a post.
 	PostParams struct {
-		Title    string  `json:"title"`
-		Content  string  `json:"body"`
-		Font     string  `json:"font"`
-		IsRTL    *bool   `json:"rtl"`
-		Language *string `json:"lang"`
+		// Parameters only for creating
+		ID    string `json:"-"`
+		Token string `json:"token,omitempty"`
 
-		Crosspost []map[string]string `json:"crosspost"`
+		// Parameters for creating or updating
+		Title    string  `json:"title,omitempty"`
+		Content  string  `json:"body,omitempty"`
+		Font     string  `json:"font,omitempty"`
+		IsRTL    *bool   `json:"rtl,omitempty"`
+		Language *string `json:"lang,omitempty"`
+
+		Crosspost []map[string]string `json:"crosspost,omitempty"`
 	}
 )
 
 func (c *Client) GetPost(id string) (*Post, error) {
 	p := &Post{}
 	env, err := c.get(fmt.Sprintf("/posts/%s", id), p)
 	if err != nil {
 		return nil, err
 	}
 
 	var ok bool
 	if p, ok = env.Data.(*Post); !ok {
 		return nil, fmt.Errorf("Wrong data returned from API.")
 	}
 	status := env.Code
 
 	if status == http.StatusOK {
 		return p, nil
 	} else if status == http.StatusNotFound {
 		return nil, fmt.Errorf("Post not found.")
 	} else if status == http.StatusGone {
 		return nil, fmt.Errorf("Post unpublished.")
 	} else {
 		return nil, fmt.Errorf("Problem getting post: %s. %v\n", status, err)
 	}
 	return p, nil
 }
 
 func (c *Client) CreatePost(sp *PostParams) (*Post, error) {
 	p := &Post{}
 	env, err := c.post("/posts", sp, p)
 	if err != nil {
 		return nil, err
 	}
 
 	var ok bool
 	if p, ok = env.Data.(*Post); !ok {
 		return nil, fmt.Errorf("Wrong data returned from API.")
 	}
 
 	status := env.Code
 	if status == http.StatusCreated {
 		return p, nil
 	} else if status == http.StatusBadRequest {
 		return nil, fmt.Errorf("Bad request: %s", env.ErrorMessage)
 	} else {
 		return nil, fmt.Errorf("Problem getting post: %s. %v\n", status, err)
 	}
 	return p, nil
 }
+
+func (c *Client) UpdatePost(sp *PostParams) (*Post, error) {
+	p := &Post{}
+	env, err := c.post(fmt.Sprintf("/posts/%s", sp.ID), sp, p)
+	if err != nil {
+		return nil, err
+	}
+
+	var ok bool
+	if p, ok = env.Data.(*Post); !ok {
+		return nil, fmt.Errorf("Wrong data returned from API.")
+	}
+
+	status := env.Code
+	if status == http.StatusOK {
+		return p, nil
+	} else if c.isNotLoggedIn(status) {
+		return nil, fmt.Errorf("Not authenticated.")
+	} else if status == http.StatusBadRequest {
+		return nil, fmt.Errorf("Bad request: %s", env.ErrorMessage)
+	} else {
+		return nil, fmt.Errorf("Problem getting post: %s. %v\n", status, err)
+	}
+	return p, nil
+}
diff --git a/post_test.go b/post_test.go
index 6c4ad14..d70be40 100644
--- a/post_test.go
+++ b/post_test.go
@@ -1,44 +1,56 @@
 package writeas
 
 import (
 	"testing"
 
 	"strings"
 )
 
 func TestCreatePost(t *testing.T) {
 	wac := NewClient()
 	p, err := wac.CreatePost(&PostParams{
 		Title:   "Title!",
 		Content: "This is a post.",
 		Font:    "sans",
 	})
 	if err != nil {
 		t.Errorf("Post create failed: %v", err)
-	} else {
-		t.Logf("Post created: %+v", p)
+		return
+	}
+	t.Logf("Post created: %+v", p)
+
+	// Update post
+	p, err = wac.UpdatePost(&PostParams{
+		ID:      p.ID,
+		Token:   p.Token,
+		Content: "Now it's been updated!",
+	})
+	if err != nil {
+		t.Errorf("Post update failed: %v", err)
+		return
 	}
+	t.Logf("Post updated: %+v", p)
 }
 
 func TestGetPost(t *testing.T) {
 	wac := NewClient()
 
 	res, err := wac.GetPost("zekk5r9apum6p")
 	if err != nil {
 		t.Errorf("Unexpected fetch results: %+v, err: %v\n", res, err)
 	} else {
 		t.Logf("Post: %+v", res)
 		if res.Content != "This is a post." {
 			t.Errorf("Unexpected fetch results: %+v\n", res)
 		}
 	}
 
 	res, err = wac.GetPost("3psnxyhqxy3hq")
 	if err != nil {
 		t.Errorf("Unexpected fetch results: %+v, err: %v\n", res, err)
 	} else {
 		if !strings.HasPrefix(res.Content, "                               Write.as Blog") {
 			t.Errorf("Unexpected fetch results: %+v\n", res)
 		}
 	}
 }