Sixteen patients with biliary atresia and 11 patients with neonatal hepatitis were studied preoperatively with either Tc-99m-diethyl-IDA or TC-99m-diisopropyl-IDA. Two parameters were evaluated: hepatocyte clearance and time to appearance of radioactivity in the intestine. Two observers, using a visual grading system of 1 to 4, gave the 16 patients with biliary atresia a hepatocyte clearance grade of 1.7 +/- 0.6 (mean +/- SD); intestinal radioactivity was not seen through 24 hours. The hepatocyte clearance grade of the 11 patients with neonatal hepatitis was 2.1 +/- 0.9 (mean +/- SD) (p greater than 0.05); intestinal radioactivity was seen in nine of 11 patients (p less than 0.001). Using both parameters, 91% of the patients were classified correctly, 4% were misclassified, and 6% were classified as indeterminate; sensitivity and specificity for biliary atresia were 97% and 82%, respectively. Radionuclide imaging with the newer technetium-99m-labeled hepatobiliary radiopharmaceuticals appears promising for the noninvasive diagnosis of biliary atresia.