diff --git a/ui.go b/ui.go
index 33c1263..fb120a2 100644
--- a/ui.go
+++ b/ui.go
@@ -27,20 +27,34 @@ type Ui interface {
 	// Output is called for normal standard output.
 	Output(string)
 
+	// Outputf calls Output with a format specifier.
+	Outputf(string, ...interface{})
+
 	// Info is called for information related to the previous output.
 	// In general this may be the exact same as Output, but this gives
 	// Ui implementors some flexibility with output formats.
 	Info(string)
 
+	// Infof calls Info with a format specifier.
+	Infof(string, ...interface{})
+
 	// Error is used for any error messages that might appear on standard
 	// error.
 	Error(string)
 
+	// Errorf calls Error with a format specifier.
+	Errorf(string, ...interface{})
+
 	// Warn is used for any warning messages that might appear on standard
 	// error.
 	Warn(string)
+
+	// Warnf calls Warn with a format specifier.
+	Warnf(string, ...interface{})
 }
 
+var _ Ui = &BasicUi{}
+
 // BasicUi is an implementation of Ui that just outputs to the given
 // writer. This UI is not threadsafe by default, but you can wrap it
 // in a ConcurrentUi to make it safe.
@@ -116,19 +130,37 @@ func (u *BasicUi) Error(message string) {
 	fmt.Fprint(w, "\n")
 }
 
+func (u *BasicUi) Errorf(format string, a ...interface{}) {
+	u.Error(fmt.Sprintf(format, a...))
+}
+
 func (u *BasicUi) Info(message string) {
 	u.Output(message)
 }
 
+func (u *BasicUi) Infof(format string, a ...interface{}) {
+	u.Info(fmt.Sprintf(format, a...))
+}
+
 func (u *BasicUi) Output(message string) {
 	fmt.Fprint(u.Writer, message)
 	fmt.Fprint(u.Writer, "\n")
 }
 
+func (u *BasicUi) Outputf(format string, a ...interface{}) {
+	u.Output(fmt.Sprintf(format, a...))
+}
+
 func (u *BasicUi) Warn(message string) {
 	u.Error(message)
 }
 
+func (u *BasicUi) Warnf(format string, a ...interface{}) {
+	u.Warn(fmt.Sprintf(format, a...))
+}
+
+var _ Ui = &PrefixedUi{}
+
 // PrefixedUi is an implementation of Ui that prefixes messages.
 type PrefixedUi struct {
 	AskPrefix       string
@@ -164,6 +196,10 @@ func (u *PrefixedUi) Error(message string) {
 	u.Ui.Error(message)
 }
 
+func (u *PrefixedUi) Errorf(format string, a ...interface{}) {
+	u.Error(fmt.Sprintf(format, a...))
+}
+
 func (u *PrefixedUi) Info(message string) {
 	if message != "" {
 		message = fmt.Sprintf("%s%s", u.InfoPrefix, message)
@@ -172,6 +208,10 @@ func (u *PrefixedUi) Info(message string) {
 	u.Ui.Info(message)
 }
 
+func (u *PrefixedUi) Infof(format string, a ...interface{}) {
+	u.Info(fmt.Sprintf(format, a...))
+}
+
 func (u *PrefixedUi) Output(message string) {
 	if message != "" {
 		message = fmt.Sprintf("%s%s", u.OutputPrefix, message)
@@ -180,6 +220,10 @@ func (u *PrefixedUi) Output(message string) {
 	u.Ui.Output(message)
 }
 
+func (u *PrefixedUi) Outputf(format string, a ...interface{}) {
+	u.Output(fmt.Sprintf(format, a...))
+}
+
 func (u *PrefixedUi) Warn(message string) {
 	if message != "" {
 		message = fmt.Sprintf("%s%s", u.WarnPrefix, message)
@@ -187,3 +231,7 @@ func (u *PrefixedUi) Warn(message string) {
 
 	u.Ui.Warn(message)
 }
+
+func (u *PrefixedUi) Warnf(format string, a ...interface{}) {
+	u.Warn(fmt.Sprintf(format, a...))
+}
diff --git a/ui_colored.go b/ui_colored.go
index e3d5131..e2e499c 100644
--- a/ui_colored.go
+++ b/ui_colored.go
@@ -21,6 +21,8 @@ var (
 	UiColorCyan            = UiColor{36, false}
 )
 
+var _ Ui = &ColoredUi{}
+
 // ColoredUi is a Ui implementation that colors its output according
 // to the given color schemes for the given type of output.
 type ColoredUi struct {
@@ -43,18 +45,34 @@ func (u *ColoredUi) Output(message string) {
 	u.Ui.Output(u.colorize(message, u.OutputColor))
 }
 
+func (u *ColoredUi) Outputf(format string, a ...interface{}) {
+	u.Output(fmt.Sprintf(format, a...))
+}
+
 func (u *ColoredUi) Info(message string) {
 	u.Ui.Info(u.colorize(message, u.InfoColor))
 }
 
+func (u *ColoredUi) Infof(format string, a ...interface{}) {
+	u.Info(fmt.Sprintf(format, a...))
+}
+
 func (u *ColoredUi) Error(message string) {
 	u.Ui.Error(u.colorize(message, u.ErrorColor))
 }
 
+func (u *ColoredUi) Errorf(format string, a ...interface{}) {
+	u.Error(fmt.Sprintf(format, a...))
+}
+
 func (u *ColoredUi) Warn(message string) {
 	u.Ui.Warn(u.colorize(message, u.WarnColor))
 }
 
+func (u *ColoredUi) Warnf(format string, a ...interface{}) {
+	u.Warn(fmt.Sprintf(format, a...))
+}
+
 func (u *ColoredUi) colorize(message string, color UiColor) string {
 	if color.Code == -1 {
 		return message
diff --git a/ui_concurrent.go b/ui_concurrent.go
index b4f4dbf..8639d29 100644
--- a/ui_concurrent.go
+++ b/ui_concurrent.go
@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"fmt"
 	"sync"
 )
 
@@ -32,6 +33,10 @@ func (u *ConcurrentUi) Error(message string) {
 	u.Ui.Error(message)
 }
 
+func (u *ConcurrentUi) Errorf(format string, a ...interface{}) {
+	u.Error(fmt.Sprintf(format, a...))
+}
+
 func (u *ConcurrentUi) Info(message string) {
 	u.l.Lock()
 	defer u.l.Unlock()
@@ -39,6 +44,10 @@ func (u *ConcurrentUi) Info(message string) {
 	u.Ui.Info(message)
 }
 
+func (u *ConcurrentUi) Infof(format string, a ...interface{}) {
+	u.Info(fmt.Sprintf(format, a...))
+}
+
 func (u *ConcurrentUi) Output(message string) {
 	u.l.Lock()
 	defer u.l.Unlock()
@@ -46,9 +55,17 @@ func (u *ConcurrentUi) Output(message string) {
 	u.Ui.Output(message)
 }
 
+func (u *ConcurrentUi) Outputf(format string, a ...interface{}) {
+	u.Output(fmt.Sprintf(format, a...))
+}
+
 func (u *ConcurrentUi) Warn(message string) {
 	u.l.Lock()
 	defer u.l.Unlock()
 
 	u.Ui.Warn(message)
 }
+
+func (u *ConcurrentUi) Warnf(format string, a ...interface{}) {
+	u.Warn(fmt.Sprintf(format, a...))
+}
diff --git a/ui_mock.go b/ui_mock.go
index c467728..670ef8a 100644
--- a/ui_mock.go
+++ b/ui_mock.go
@@ -40,10 +40,14 @@ func (u *MockUi) Error(message string) {
 	fmt.Fprint(u.ErrorWriter, "\n")
 }
 
+func (u *MockUi) Errorf(format string, a ...interface{}) {}
+
 func (u *MockUi) Info(message string) {
 	u.Output(message)
 }
 
+func (u *MockUi) Infof(format string, a ...interface{}) {}
+
 func (u *MockUi) Output(message string) {
 	u.once.Do(u.init)
 
@@ -51,6 +55,8 @@ func (u *MockUi) Output(message string) {
 	fmt.Fprint(u.OutputWriter, "\n")
 }
 
+func (u *MockUi) Outputf(format string, a ...interface{}) {}
+
 func (u *MockUi) Warn(message string) {
 	u.once.Do(u.init)
 
@@ -58,6 +64,8 @@ func (u *MockUi) Warn(message string) {
 	fmt.Fprint(u.ErrorWriter, "\n")
 }
 
+func (u *MockUi) Warnf(format string, a ...interface{}) {}
+
 func (u *MockUi) init() {
 	u.ErrorWriter = new(bytes.Buffer)
 	u.OutputWriter = new(bytes.Buffer)