A prospective series of 220 patients with jaundice and/or cholestasis was analysed by means of discriminant analysis to evaluate the diagnostic value of various symptoms and signs and basic hepatopancreatobiliary laboratory tests in the differential diagnosis of these patients. In addition, a computer-based diagnostic score (DS) system was developed and compared with the diagnostic value of clinical evaluation (CE), ultrasound (US), computed tomography (CT), and endoscopic retrograde cholangiopancreatography (ERCP). A multivariate stepwise discriminant analysis showed five independent diagnostic factors in distinguishing extrahepatic and intrahepatic diseases: duration of jaundice (p = 0.002), serum protein concentrations (p = 0.002), Normotest (p = 0.04), fever during the past 3 months (p = 0.54), and age (p = 0.58). To sum up the contributions of independent factors, a DS was developed. The discrimination function was as follows: duration of jaundice x 0.97 + age x -0.40 + fever during the past 3 months x 0.33 + serum protein concentration x 0.35 + Normotest x -0.27. The diagnostic sensitivity of DS in the detection of extrahepatic disease was 96%, with a specificity of 80% and an efficiency of 93%. The sensitivities of the imaging methods (62-85%) were inferior to that of DS, whereas the specificities were better (94-98%). The sensitivity of CE was only slightly lower (86%) than that of DS, but the specificity was lowest (57%). In conclusion, relatively few (5 of 40) of the classical symptoms, signs, and biochemical tests proved to be independent diagnostic factors in distinguishing extrahepatic and intrahepatic diseases.(ABSTRACT TRUNCATED AT 250 WORDS)