could be arthritis - a chiropractor told me that if you can get a repeated crack over and over in the exact same way (turning your head to one side, or whatever), it could be arthritis. but mostly likely it's not. more likely things are slightly out of alignment, and/or you have muscle tension which is pulling on your vertabrae. if you can afford it, a trip or two to a chiropractor works wonders! it eliminated a lot of my neck cracking, not to mention neck soreness, tight shoulders, and headaches.