Acute renal failure developed in an elderly woman with a rapidly progressive illness characterized by nuchal rigidity, limb spasm, repetitive grunting vocalizations without intelligible speech, and risus sardonicus. Eventually she developed characteristic findings of increased tone in her masseter muscles (trismus) and rigid upper and lower extremities, consistent with generalized tetanus. Increasing serum creatinine was temporally associated with rising creatine phosphokinase (CPK) and striking elevations of plasma myoglobin. The patient had marked lability of blood pressure and pulse. She improved briefly after tetanus toxoid and broad-spectrum antibiotics, but died of heart failure after 9 days of hospitalization. A necrotic pelvic tumor was believed to be the source of infection. Tetanus is a preventable disease, which has not been eradicated, even in Western populations. Full-blown tetanus has a high fatality rate, and should be considered in the differential diagnosis of acute renal failure in the setting of rising CPK and continued release of muscle myoglobin.