The present investigation was aimed to assess the usefulness of biliary agents scintigraphy in the diagnosis of hepatocellular carcinoma (HCC) and to ascertain the relationship between the uptake of these agents and the degree of HCC differentiation. Forty-four patients with this hepatic cancer were included in the study. Liver scans were performed 20 min and 3 hr after the administration of 99mTc diisopropyliminodiacetic acid (DISIDA). DISIDA scintigraphy could not be assessed in six cases. In 16 (42%) out of the remaining 38 patients, the tumor exhibited equal or greater radioactivity uptake than the surrounding liver. In six out of these 16 patients, tumor uptake was apparent in the early and delayed hepatic scans, while in the other ten subjects radioactivity uptake by the HCC could only be detected in the 3-hr delayed scans. In the remaining 22 patients, HCC appeared as a cold area. Tumor location by this technique did not differ from that observed by 99mTc-sulfur colloid scan or ultrasound. DISIDA uptake was significantly related to tumor differentiation: 70% of those well differentiated tumors exhibited DISIDA uptake, whereas it was found in only 30% of those moderately differentiated and in none of those poorly differentiated (p less than 0.05). These results show that DISIDA scintigraphy can be useful in the diagnosis of HCC. Since its sensitivity is related to the degree of tumor differentiation, it may be indicated when aspiration cytology is unable to distinguish between well differentiated HCC and reactive changes due to hepatic cirrhosis.