Detection of small hepatocellular carcinoma (HCC) eligible for curative treatment is increased by surveillance, but its optimal periodicity is still debated. Thus, this randomized trial compared two ultrasonographic (US) periodicities: 3 months versus 6 months. A multicenter randomized trial was conducted in France and Belgium (43 sites). Patients with histologically proven compensated cirrhosis were randomized into two groups: US every 6 months (Gr6M) or 3 months (Gr3M). For each focal lesion detected, diagnostic procedures were performed according to European Association for the Study of the Liver guidelines. Cumulative incidence of events was estimated, then compared using Gray's test. The prevalence of HCC ≤30 mm in diameter was the main endpoint. A sample size of 1,200 patients was required. A total of 1,278 patients were randomized (Gr3M, n = 640; Gr6M, n = 638; alcohol 39.2%, hepatitis C virus 44.1%, hepatitis B virus 12.5%). At least one focal lesion was detected in 358 patients (28%) but HCC was confirmed in only 123 (9.6%) (uninodular 58.5%, ≤30 mm in diameter 74%). Focal-lesion incidence was not different between Gr3M and Gr6M groups (2-year estimates, 20.4% versus 13.2%, P = 0.067) but incidence of lesions ≤10 mm was increased (41% in Gr3M versus 28% in Gr6M, P = 0.002). No difference in either HCC incidence (P = 0.13) or in prevalence of tumors ≤30 mm in diameter (79% versus 70%, P = 0.30) was observed between the randomized groups. Conclusion: US surveillance, performed every 3 months, detects more small focal lesions than US every 6 months, but does not improve detection of small HCC, probably because of limitations in recall procedures. (HEPATOLOGY 2011;)