During a disk operation, the wound was flushed with hydrogen peroxide, resulting in a blackish brown discoloration of the musculature without the formation of foam. Clinical observation caused the experienced biochemist to make the diagnosis of suspected acatalasia, a rare congenital metabolic defect which is inherited autosomally recessively. Investigation of the catalase activity in the hemolysate of the patient and his brother confirmed this suspicion and resulted in the first diagnosis of this condition in Austria.