Follow-up studies using monitoring with alpha1-feto protein (AFP), ultrasonography (US), and computed tomography (CT) were carried out in 75 patients who had prior partial hepatectomy for hepatocellular carcinoma (HCC). Recurrence in the remaining liver was confirmed in 31 patients (41.3%) during the 4 month to 3 years 7 month period. Ultrasonography detected recurrence in 29 cases (sensitivity: 93.5%), CT in 26 (83.9%), and AFP assay in 12 (38.7%). In 4 patients, ultrasonography detected four recurrent nodules that CT missed. In 1 patient, two subphrenic nodules were detected with CT but not with ultrasonography. The specificity of US, CT, and AFP assay was 90.9%, 95.5%, and 93.2% respectively. Frequent follow-up study with ultrasonography in combination with CT and AFP assay should be recommended for the early detection of recurrent HCC. Ultrasonography is mandatory for the follow-up of patients with a prior hepatectomy for HCC.