The chemical synthesis of an iminodiacetic-acid-substituted tetrabromo-o-cresolphthalein (BP-IDA), which complexes 68Ga tightly. The liver uptake, bile excretion and urinary excretion of the complex were examined in rats. Maximum liver uptake reached 60%, and 1-h cumulative bile excretion was 75% of injected dose. Urinary excretion in rats with ligated common bile duct remained below 1%. Competitive action of exogenous bilirubin on hepatobiliary excretion of the Ga complex was less pronounced than that of bromosulfophthalein. The absolute activity determination of the positron emitter 68Ga, the high accumulation in the liver, the low urinary excretion and the weak competition from exogenous bilirubin are promising features of this radiopharmaceutical for the quantitative study of hepatobiliary function.