Iatrogenic jaundice was classified into three types according to the abnormal processes involved, namely (1) hepatocellular damage, (2) cholestasis, or (3) hemolysis. Clinical features were of little value in distinguishing among the three types. It was possible to differentiate them by laboratory tests, and the results agreed well with the histological findings. Cholestatic jaundice was frequent but mild; associated alterations in the bile canaliculi were visible by electron microscope. Hepatocellular damage was uncommon but likely to be fatal; it was characterized by cytoplasmic alterations visible by electron microscope. Treatment was similar to that for viral hepatitis and included the use of steroids. Prevention depends on developing and prescribing drugs that will cause fewer untoward reactions.