Twenty-two patients with cirrhosis and minute hepatocellular carcinoma less than 3 cm in diameter were followed for periods of 6-37 mo without specific treatment. The survival curve drawn by the Kaplan-Meier method showed a 1-yr survival of 90.7%, a 2-yr survival of 55.0%, and a 3-yr survival of 12.8%. The ultrasonic patterns of these masses in the liver were correlated with the size and showed a tendency to change from a low echo pattern to a low periphery and, finally, to a massive pattern. The growth speed calculated from the doubling time for tumor volume varied considerably from case to case with an average of 6.5 +/- 5.7 mo; it also changed in some cases during the observation period. Serum alpha-fetoprotein levels were generally low, rarely assisted in diagnosis, but tended to increase when the mass attained a diameter of greater than 3 cm; sudden acceleration in the rate of increase in alpha-fetoprotein level often coincided with a change of ultrasonic pattern to the massive one.