We performed periodical examinations by ultrasonography (US) and serum alpha-fetoprotein in 272 patients with liver cirrhosis (male, 167; female, 105) over long follow-up periods (1985. 1-1992.9). The average period was 1934 days, and we prospectively studied the early detection of hepatocellular carcinoma (HCC). HCC was detected in 78 patients during the periods, with the average cumulative incidence rate being per year 7%. Tumor size at detection was 15mm or less in diameter in 37.2% HCC patients and 30mm or less in 89.7%. In spite of frequent ultrasonic examinations, it was difficult to detect small sized HCCs in blind spots of US or in the liver with the rough parenchymal echo pattern. Predictive factors important for development of HCC were analyzed using Cox's proportional hazards model. It showed that significant factors were serum AFP level, liver parenchymal echo pattern and small mass lesions (ultrasonic appearance) of the liver.