AMA Motocross Championship
The AMA Motocross Championship begins in mid May and continues until late August. The championship consists of twelve rounds at twelve major tracks all over the continental United States. There are three classes: the 250cc Motocross Class for 150–250 cc 4-stroke machines, the 450cc Motocross Class for 251–450 cc 4-stroke machines and a 250cc Women's Class, using the same rules as men's 250cc.