Four consecutive cases of proven hepatocellular carcinoma (HCC) showed significant avidity of 99mTc -labeled iminodiacetic acids (Tc- IDAs ) in preoperative scintigraphy. In one patient, the pulmonary metastasis showed uptake of Tc-IDA. Such scintigraphic findings were obvious only in the delayed scans, performed 2 1/2-4 hr after injection. Since Tc- IDAs and bilirubin are functional analogs physiologically, the ability of HCC to concentrate Tc- IDAs may be related to the ability of HCC neoplastic cells to form bile intracellularly. This hypothesis is supported by the fact that intracellular bile granules were found in the tumor cells of all four patients. This suggests a potential for using Tc- IDAs for the specific and preoperative diagnostic of HCC.