We present details of two separate nodular lesions of atypical adenomatous hyperplasia, within one of which a small area of overt hepatocellular carcinoma was detected. The patient was positive for serum hepatitis B surface antigen, and Southern blot analysis revealed that deoxyribonucleic acid from the lesions of hepatocellular carcinoma and surrounding atypical adenomatous hyperplasia showed the same restriction pattern of integrated hepatitis B virus deoxyribonucleic acid, indicating that the two lesions were derived from an identical clone. It was also indicated that the two separate lesions of atypical adenomatous hyperplasia were independently derived through clonal expansion of different cells.