Outbreaks of exertional rhabdomyolysis with acute renal impairment which occurred in New York City (NYC) and Massachusetts in 1988 were discussed. One fatality and three hospitalizations among candidates for the NYC Fire Department (NYCFD) were reported to the NYC Department of Health. Rhabdomyolysis developed after the candidates participated in the NYCFD physical fitness test. The fitness test was then modified to include medical screening, controlled temperature, and adequate hydration. Despite these interventions, additional hospitalizations for rhabdomyolysis and renal impairment occurred. During a 19 month period, 0.2% of the 16,506 candidates required hospitalization. Four individuals had rhabdomyolysis, 16 suffered from renal impairment, and 12 were afflicted with both rhabdomyolysis and renal impairment. A case control study found that risk factors for rhabdomyolysis and/or renal impairment included an underlying medical condition and the lack of regular physical activity. The Massachusetts Department of Health was notified that five of 50 police trainees were hospitalized for severe dehydration, rhabdomyolysis, and renal impairment during a physical training program which included a mental stress component. Rhabdomyolysis was evident in all 50 trainees, of whom 66% had severe rhabdomyolysis. Overall, 13 trainees were hospitalized, of whom 69% had renal insufficiency. A combination of heat stroke, rhabdomyolysis, and kidney and liver failure resulted in one fatality. Trainees who failed either the cardiovascular fitness or muscle strength test were at an increased risk of severe rhabdomyolysis or renal impairment. Recommendations included the meeting of fitness requirements by all trainees before and during training, the supplying of adequate hydration during training, and the implementation of a clear approach to injury prevention. The authors conclude that the safety of trainees and candidates must be considered during physical performance testing. Physicians and occupational health consultants should be cognizant of the hazards associated with exertional rhabdomyolysis and renal impairment.