A prospective study examining the epidemiology of blisters and, in particular, the association of blisters with subsequent injuries was conducted involving 2,130 male US Marine Corps recruits participating in initial physical training at the Marine Corps Recruit Depot in San Diego, California. From January 1993 through September 1994, recruits experienced an incidence of 2.05 blisters per 100 recruit-months. Recruits with blisters were 50% more likely to experience an additional training-related injury. Blisters, in combination with other related injuries, resulted in 159 clinic visits, 103 days of assigned light duty, and 177 lost days of training. This loss of time cost a minimum of $29,529. Extrapolating to the annual population of recruits, this represents an approximate annual expense of $690,000. Aggressive blister prevention and management in this setting has the potential to greatly reduce morbidity and fiscal costs.