Hepatitis B virus (HBV) genotype C is predominant in Japan. However, many HBV subtypes are involved in each genotype, and the clinical manifestations in the patients associated with each subtype remain unknown. Therefore, we investigated the relationship between HBV subtype and clinical aspects of chronic HBV infection. The subtype of 237 patients with chronic HBV infection, including 74 asymptomatic carriers, was determined. The subtypes of 110 HBV carriers undergoing long-term follow-up management were determined twice to detect subtypic changes. The clinical features of the patients were also studied with regard to presence or absence of subtypic change. The subtypic distribution in the 237 HBV carriers was as follows: subtype adr, 161 (68%); subtype adw, 25 (11%); subtype adwr, 12 (5%); subtype ar, 24 (10%); subtype adyr, 4 (2%); and unclassified, 8 (3%). The proportion of asymptomatic carriers in patients with subtype adw was significantly higher than those in patients with subtype adr (56% vs. 28%, P < 0.05). In addition, the proportion of HCC in patients with subtype adwr was significantly higher than those in patients with subtype adr (25% vs. 6%, P < 0.05). The prevalence of subtype adr in 74 asymptomatic carriers tended to decrease with age (82% in carriers aged < or =35 years vs 43% in those aged > or =61 years, P < 0.05). The subtypic change and the course of chronic HBV infection had no significant correlation. These results suggest that HBV subtypes are associated with the clinical course of chronic HBV infection.