There are three ways to kill a program / process under Mac OS X. These are using Force Quit from the Apple Menu, Quitting the process in Activity Monitor (Utilities folder), and killing the process from the command line using the Terminal application (Utilities folder.)

Using Force Quit from the Apple Menu

The most common method used to close a program that is not responding is to select Force Quit from the Apple Menu. A window will appear listing all the user applications running on the system. Applications running normally will appear as black text, whereas applications that are hung or having trouble will appear as red text. Highlight the application you want to kill and click on the Force Quit button that appears at the bottom of the window.

Quitting A Process Using Activity Monitor

You can also quit a process using the Activity Monitor application (found in the Utilities folder and pictured below) Note: This function is only available in Mac OS 10.3 and later. Launch Activity Monitor, highlight the program you want to kill, and then click on the Quit Process button in the tool bar at the top of the Activity Monitor window.

Killing A Process from the Command Prompt Using Terminal

Another way to kill applications is to open a terminal window using the Terminal application (Utilities folder). At the command prompt type: (Be sure that all the characters are lowercase and a space is present between top and -u.)

top -u

Then press Enter/Return on your keyboard. A list of the top processes will appear in the window. Identify which process you wish to kill and note the PID or Process ID for that process and then type:

q

Press Enter/Return on your keyboard.

Then type:

kill -9

followed by a space and the PID and then press Enter/Return on your keyboard. For example, to kill a process that has a PID of 28598 then you would type:

kill -9 28598

Then press Enter/Return on your keyboard.

This will almost always kill the process. If the system says you do not have sufficient privileges, then add sudo before the kill command. You would type:

sudo kill -9

followed by a space and the PID and then press Enter/Return on your keyboard. sudo enables you to type in a system command and it will prompt you for the system administrator password before executing the command. Type in your password and the system will kill the process.