Evaluation of the jaundiced patient''s condition frequently can be difficult. Clinical history, physical examination, liver function tests and other laboratory data are often inconclusive in differentiating extrahepatic obstruction (surgical jaundice) from intrahepatic cholestasis (medical jaundice). During a 14-mo. period, 40 cases of jaundice of unknown causes were evaluated. Ultrasound was able to correctly diagnose pathologically proved extrahepatic obstruction in 23 of 24 patients and intrahepatic cholestasis in 15 of 16 patients. There was 1 false-positive and 1 false-negative result in this series.