diff --git a/src/lib.rs b/src/lib.rs
index 2d958f6..eb275e8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,7 +2,7 @@
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![allow(unused_features)]
-#![feature(core, libc, std_misc)]
+#![feature(collections, core, libc, std_misc)]
 
 //! This is a library for getting information on Unix users and groups.
 //!
@@ -92,7 +92,7 @@
 //! ```rust
 //! use users::{Users, OSUsers};
 //! let mut cache = OSUsers::empty_cache();
-//! match cache.get_group_by_name("admin".to_string()) {
+//! match cache.get_group_by_name("admin") {
 //!     None => {},
 //!     Some(group) => {
 //!         println!("The '{}' group has the ID {}", group.name, group.gid);
@@ -116,6 +116,9 @@
 extern crate libc;
 use libc::{c_char, c_int, uid_t, gid_t, time_t};
 
+extern crate collections;
+use collections::borrow::ToOwned;
+
 use std::ffi::CStr;
 use std::ptr::read;
 use std::str::from_utf8_unchecked;
@@ -131,13 +134,13 @@ pub trait Users {
     fn get_user_by_uid(&mut self, uid: i32) -> Option<User>;
 
     /// Return a User object if one exists for the given username; otherwise, return None.
-    fn get_user_by_name(&mut self, username: String) -> Option<User>;
+    fn get_user_by_name(&mut self, username: &str) -> Option<User>;
 
     /// Return a Group object if one exists for the given group ID; otherwise, return None.
     fn get_group_by_gid(&mut self, gid: u32) -> Option<Group>;
 
     /// Return a Group object if one exists for the given groupname; otherwise, return None.
-    fn get_group_by_name(&mut self, group_name: String) -> Option<Group>;
+    fn get_group_by_name(&mut self, group_name: &str) -> Option<Group>;
 
     /// Return the user ID for the user running the process.
     fn get_current_uid(&mut self) -> i32;
@@ -295,8 +298,10 @@ impl Users for OSUsers {
         }
     }
 
-    fn get_user_by_name(&mut self, username: String) -> Option<User> {
-        match self.users_back.entry(username.clone()) {
+    fn get_user_by_name(&mut self, username: &str) -> Option<User> {
+        // to_owned() could change here:
+        // https://github.com/rust-lang/rfcs/blob/master/text/0509-collections-reform-part-2.md#alternatives-to-toowned-on-entries
+        match self.users_back.entry(username.to_owned()) {
             Vacant(entry) => {
                 let user = unsafe { passwd_to_user(getpwnam(username.as_ptr() as *const i8)) };
                 match user {
@@ -338,8 +343,10 @@ impl Users for OSUsers {
         }
     }
 
-    fn get_group_by_name(&mut self, group_name: String) -> Option<Group> {
-        match self.groups_back.clone().entry(group_name.clone()) {
+    fn get_group_by_name(&mut self, group_name: &str) -> Option<Group> {
+        // to_owned() could change here:
+        // https://github.com/rust-lang/rfcs/blob/master/text/0509-collections-reform-part-2.md#alternatives-to-toowned-on-entries
+        match self.groups_back.clone().entry(group_name.to_owned()) {
             Vacant(entry) => {
                 let user = unsafe { struct_to_group(getgrnam(group_name.as_ptr() as *const i8)) };
                 match user {
@@ -398,7 +405,7 @@ pub fn get_user_by_uid(uid: i32) -> Option<User> {
 }
 
 /// Return a User object if one exists for the given username; otherwise, return None.
-pub fn get_user_by_name(username: String) -> Option<User> {
+pub fn get_user_by_name(username: &str) -> Option<User> {
     OSUsers::empty_cache().get_user_by_name(username)
 }
 
@@ -408,7 +415,7 @@ pub fn get_group_by_gid(gid: u32) -> Option<Group> {
 }
 
 /// Return a Group object if one exists for the given groupname; otherwise, return None.
-pub fn get_group_by_name(group_name: String) -> Option<Group> {
+pub fn get_group_by_name(group_name: &str) -> Option<Group> {
     OSUsers::empty_cache().get_group_by_name(group_name)
 }
 
diff --git a/src/mock.rs b/src/mock.rs
index 1f63110..a97f907 100644
--- a/src/mock.rs
+++ b/src/mock.rs
@@ -86,7 +86,7 @@ impl Users for MockUsers {
     	self.users.get(&uid).cloned()
     }
 
-    fn get_user_by_name(&mut self, username: String) -> Option<User> {
+    fn get_user_by_name(&mut self, username: &str) -> Option<User> {
 		self.users.values().find(|u| u.name == username).cloned()
     }
 
@@ -94,7 +94,7 @@ impl Users for MockUsers {
     	self.groups.get(&gid).cloned()
     }
 
-    fn get_group_by_name(&mut self, group_name: String) -> Option<Group> {
+    fn get_group_by_name(&mut self, group_name: &str) -> Option<Group> {
     	self.groups.values().find(|g| g.name == group_name).cloned()
     }
 
@@ -135,14 +135,14 @@ mod test {
 	fn username() {
 		let mut users = MockUsers::with_current_uid(1337);
 		users.add_user(User { uid: 1440, name: "fred".to_string(), primary_group: 101 });
-		assert_eq!(Some(1440), users.get_user_by_name("fred".to_string()).map(|u| u.uid))
+		assert_eq!(Some(1440), users.get_user_by_name("fred").map(|u| u.uid))
 	}
 
 	#[test]
 	fn no_username() {
 		let mut users = MockUsers::with_current_uid(1337);
 		users.add_user(User { uid: 1440, name: "fred".to_string(), primary_group: 101 });
-		assert_eq!(None, users.get_user_by_name("criminy".to_string()).map(|u| u.uid))
+		assert_eq!(None, users.get_user_by_name("criminy").map(|u| u.uid))
 	}
 
 	#[test]
@@ -162,14 +162,14 @@ mod test {
 	fn group_name() {
 	    let mut users = MockUsers::with_current_uid(0);
 		users.add_group(Group { gid: 1337, name: "fred".to_string(), members: vec![], });
-		assert_eq!(Some(1337), users.get_group_by_name("fred".to_string()).map(|g| g.gid))
+		assert_eq!(Some(1337), users.get_group_by_name("fred").map(|g| g.gid))
 	}
 
 	#[test]
 	fn no_group_name() {
 	    let mut users = MockUsers::with_current_uid(0);
 		users.add_group(Group { gid: 1337, name: "fred".to_string(), members: vec![], });
-		assert_eq!(None, users.get_group_by_name("santa".to_string()).map(|g| g.gid))
+		assert_eq!(None, users.get_group_by_name("santa").map(|g| g.gid))
 	}
 
 	#[test]