diff --git a/github/repos_collaborators.go b/github/repos_collaborators.go
index 3ad6162..61dc4ef 100644
--- a/github/repos_collaborators.go
+++ b/github/repos_collaborators.go
@@ -22,6 +22,8 @@ func (s *RepositoriesService) ListCollaborators(owner, repo string, opt *ListOpt
 		return nil, nil, err
 	}
 
+	req.Header.Set("Accept", mediaTypeOrgPermissionPreview)
+
 	users := new([]User)
 	resp, err := s.client.Do(req, users)
 	if err != nil {
@@ -49,15 +51,33 @@ func (s *RepositoriesService) IsCollaborator(owner, repo, user string) (bool, *R
 	return isCollab, resp, err
 }
 
+// RepositoryAddCollaboratorOptions specifies the optional parameters to the
+// RepositoriesService.AddCollaborator method.
+type RepositoryAddCollaboratorOptions struct {
+	// Permission specifies the permission to grant the user on this repository.
+	// Possible values are:
+	//     pull - team members can pull, but not push to or administer this repository
+	//     push - team members can pull and push, but not administer this repository
+	//     admin - team members can pull, push and administer this repository
+	//
+	// Default value is "pull".  This option is only valid for organization-owned repositories.
+	Permission string `json:"permission,omitempty"`
+}
+
 // AddCollaborator adds the specified Github user as collaborator to the given repo.
 //
 // GitHub API docs: http://developer.github.com/v3/repos/collaborators/#add-collaborator
-func (s *RepositoriesService) AddCollaborator(owner, repo, user string) (*Response, error) {
+func (s *RepositoriesService) AddCollaborator(owner, repo, user string, opt *RepositoryAddCollaboratorOptions) (*Response, error) {
 	u := fmt.Sprintf("repos/%v/%v/collaborators/%v", owner, repo, user)
-	req, err := s.client.NewRequest("PUT", u, nil)
+	req, err := s.client.NewRequest("PUT", u, opt)
 	if err != nil {
 		return nil, err
 	}
+
+	if opt != nil {
+		req.Header.Set("Accept", mediaTypeOrgPermissionPreview)
+	}
+
 	return s.client.Do(req, nil)
 }
 
diff --git a/github/repos_collaborators_test.go b/github/repos_collaborators_test.go
index de26ba9..ee6c498 100644
--- a/github/repos_collaborators_test.go
+++ b/github/repos_collaborators_test.go
@@ -6,6 +6,7 @@
 package github
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"reflect"
@@ -18,6 +19,7 @@ func TestRepositoriesService_ListCollaborators(t *testing.T) {
 
 	mux.HandleFunc("/repos/o/r/collaborators", func(w http.ResponseWriter, r *http.Request) {
 		testMethod(t, r, "GET")
+		testHeader(t, r, "Accept", mediaTypeOrgPermissionPreview)
 		testFormValues(t, r, values{"page": "2"})
 		fmt.Fprintf(w, `[{"id":1}, {"id":2}]`)
 	})
@@ -86,19 +88,29 @@ func TestRepositoriesService_AddCollaborator(t *testing.T) {
 	setup()
 	defer teardown()
 
+	opt := &RepositoryAddCollaboratorOptions{Permission: "admin"}
+
 	mux.HandleFunc("/repos/o/r/collaborators/u", func(w http.ResponseWriter, r *http.Request) {
+		v := new(RepositoryAddCollaboratorOptions)
+		json.NewDecoder(r.Body).Decode(v)
+
 		testMethod(t, r, "PUT")
+		testHeader(t, r, "Accept", mediaTypeOrgPermissionPreview)
+		if !reflect.DeepEqual(v, opt) {
+			t.Errorf("Request body = %+v, want %+v", v, opt)
+		}
+
 		w.WriteHeader(http.StatusNoContent)
 	})
 
-	_, err := client.Repositories.AddCollaborator("o", "r", "u")
+	_, err := client.Repositories.AddCollaborator("o", "r", "u", opt)
 	if err != nil {
 		t.Errorf("Repositories.AddCollaborator returned error: %v", err)
 	}
 }
 
 func TestRepositoriesService_AddCollaborator_invalidUser(t *testing.T) {
-	_, err := client.Repositories.AddCollaborator("%", "%", "%")
+	_, err := client.Repositories.AddCollaborator("%", "%", "%", nil)
 	testURLParseError(t, err)
 }
 
diff --git a/github/users.go b/github/users.go
index bd68ac2..95cca6b 100644
--- a/github/users.go
+++ b/github/users.go
@@ -59,6 +59,10 @@ type User struct {
 	// TextMatches is only populated from search results that request text matches
 	// See: search.go and https://developer.github.com/v3/search/#text-match-metadata
 	TextMatches []TextMatch `json:"text_matches,omitempty"`
+
+	// Permissions identifies the permissions that a user has on a given
+	// repository. This is only populated when calling Repositories.ListCollaborators.
+	Permissions *map[string]bool `json:"permissions,omitempty"`
 }
 
 func (u User) String() string {