A case of rhabdomyolysis is described, with onset following three intramuscular injections of loxapine and one injection of benztropine over a 7-hour period. The possible additive effects of intramuscular drug administration and psychotic episode-associated increased muscle membrane permeability are discussed. Because of the risk of acute renal failure following rhabdomyolysis, monitoring of creatine phosphokinase levels and urine tests for myoglobin are recommended for patients who develop muscular discomfort, nausea, or confusion while receiving frequent intramuscular injections of neuroleptics.