To see whether or not there is an association between the cause of cirrhosis and the number of hepatocellular carcinoma (HCC) nodules, we analyzed 178 consecutive patients in whom HCC was detected during a prospective screening by abdominal ultrasound (US). The relevant information was obtained from the database of the screening programs operating at four hospitals in the Milan area. One hundred twenty-nine (72%) patients had a single tumor nodule detected by US and 49 (28%) patients had multinodular disease. Ninety-eight (55%) patients had normal serum values of α-fetoprotein (AFP). Tumor staging with biphasic computed tomography (CT) scan or hepatic arteriography with lipiodol revealed that 101 (57%) patients had single tumor nodules and 77 (43%) patients had more than one HCC nodule. After staging, multinodular HCC was more common in patients with multiple risk factors than in the hepatitis C virus (HCV) carriers (56% vs. 38%, P = .05). Interestingly, single tumors were as common in the 126 patients undergoing 6-month interval screening as in the 52 patients who were studied at yearly intervals. The former patients, however, had more small tumors than the latter ones (91% vs. 74%, P = .04). The 22 patients who were alcohol abusers had normal levels of serum AFP more often than the hepatitis B virus (HBV) or HCV carriers or those with multiple risk factors (86% vs. 57%, P < .04; vs. 47%, P < .002; vs. 52%, P < .006, respectively). We concluded that multinodular HCC was underdetected by real time US; it prevailed among patients with multiple risk factors. In these patients, screening with US exams every 6 months may be inadequate for early detection of liver cancer.