HFS+ is a filesystem that's designed so that it shouldn't need to defragged. However, if you really need it (normal usage won't need it), iDefrag is available, although it's not free. And of course, the best way to clean up a filesystem is to wipe it and start from scratch. In short, don't worry about defragging unless you experience serious slowdown problems related to your filesystem.

Whew! Now I don't feel so guilty..Remembering back to my days in Photoshop 3.0 I think we had to do the d/f thing..Used to have plenty of crashes in those days..Love the OS X system..Crashes! Almost a thing of the past..Thanks again..RockyOne Australia

At some point your computer will begin to slow down if you never defrag your HD. Remember not matter what you use to defrag you should ALWAYS backup you complete HD before doing this as if the computer shuts down for some reason like a power outage you could mess up you entire HD. You can Defrag with TechTool Pro, Drive Genius and others but those are the two I prefer. I do this about three times a year. Depending on how much info you have on your HD and how much you use your computer will determine how much fragmentation you can develop. It can take hours to do this if you have a big HD or perhaps only an hour with a typical user. Once your start defraging do not mess with the computer until it has finished and BACKUP before you start.