To investigate the clinicopathologic features of asymptomatic carriers of hepatitis B surface antigen (HBsAg), liver biopsies were obtained in 140 carriers followed-up for more than 6 months. They included 47 older than 40 years and 75 with elevated SGPT values at least once during the follow-up period. Among the 93 carriers younger than 39 years, milder histologic changes than chronic persistent hepatitis (CPH) were seen in most of those with normal SGPT values, while more severe histologic changes (chronic lobular hepatitis, chronic active hepatitis and active cirrhosis) were found in 18 out of 50 with elevated SGPT values. In contrast, when the carriers were more than 40 years of age, the histologic liver changes became "bipolar", i.e., either very mild or quite severe, since among 47 subjects in this group, 37 (79%) had hepatic lesions milder than CPH, and the remaining 10 (21%) had cirrhosis. The positive rate of hepatitis B e antigen (HBeAg) was not significantly different among those with milder and those with more severe histologic changes in the younger group. However, that of the older carriers was significantly higher among those with liver cirrhosis (50% vs. 16.2%, p less than 0.05). The results imply that, in Taiwan where chronic HBsAg carriage usually occurs in early childhood, a poorer prognosis may exist in asymptomatic HBsAg carriers when HBeAg persists beyond the age of 40.