The diagnostic accuracy of hepatobiliary radionuclide imaging using 99mTC-labeled para-isopropyl acetanilido-iminodiacetic acid (99mTc-PIPIDA) in patients with hepatobiliary disorders was assessed in 50 patients. Thirty of the study group were jaundiced; the remaining 20 had other clinical features suggestive of some hepatobiliary disorder. The findings using PIPIDA proved to be correct in 22 (73%) of the 30 jaundiced patients and in 18 (90%) of 20 patients without jaundice. There appears to be a close relationship between the diagnostic accuracy of the test and the level of serum bilirubin. Thus, the diagnosis indicated by the PIPIDA test was correct in 30 (88%) of 34 patients in whom the serum bilirubin was less than 5 mg./dl. but only in 10 (62%) of 16 patients whose serum bilirubin exceeded 5 mg./dl. It is concluded from these observations that: 1. PIPIDA is diagnostically useful in the evaluation of hepatobiliary disorders, especially when the serum bilirubin is less than 5 mg./dl. and 2. the accuracy of this test is not absolute and the findings are not always definitive.