AbstractWe report the first case of severe thrombocytopenia occurring after ingestion of a widely used cholecystographic medium, iocetamic acid. The patient had not been given any treatment before he received the gallbladder contrast medium. Onset of symptoms was acute, and the clinical course was benign with complete recovery after one week. Bone marrow aspiration showed increased numbers of megakaryocytes, suggesting that platelets were rapidly removed from circulation. In vitro tests for antiplatelet antibodies were not performed because iocetamic acid is insoluble in aqueous solutions. Since only a few cases of thrombocytopenia following ingestion of iodine‐compounds have been reported, it seems highly unlikely that purpura will be, in the future, a major hazard in cholecystography. However, it would be wise to question patients as to any prior sensitivity to iodine before proceeding with oral cholecystography.