Physicians should be aware that the accidental ingestion of Clinitest® tablets, now in common use for urine analysis, can cause severe stricture of the esophagus because of their content of sodium hydroxide; perhaps the copper sulfate contained in the tablets may play a secondary role. The author adds a report of a case to 4 cases previously recorded. It is important that both physicians and patients realize this hazard and keep Clinitest® tablets beyond the reach of small children.