We studied 36 cases (38 nodules) of small hepatocellular carcinoma with special attention directed to detectability using angiography and histology. Among the 38 nodules, 31 nodules (81.6%) were evident. The remaining seven (18.4%) were not evident angiographically but were detected using ultrasonography and/or computed tomography, prior to angiography. An elevated level of serum alpha-fetoprotein also suggested a diagnosis of hepatocellular carcinoma. When comparisons were made between angiographically detected and undetected nodules, there was no statistically significant difference in parameters, including sex of the patient, tumor size, location of the tumor, positive rate for hepatitis B surface antigen, history of liver disease and values of alpha-fetoprotein. The small hepatocellular carcinomas not detected angiographically and evidenced only histologically had the following characteristics: (i) no fibrous capsule surrounding the nodules; (ii) well-differentiated tumors; (iii) replacing growth pattern of cancer cells, and (iv) remains of portal tracts within the tumor. The replacing growth pattern and the presence of portal tracts may correlate with the low detectability in angiography. When a definite diagnosis of angiographically undetectable tumors cannot be made using close surveillance with ultrasonography or alpha-fetoprotein and/or needle biopsy under ultrasonic guide, surgical intervention should be considered, particularly for patients at high risk for hepatocellular carcinoma.