To evaluate the relationships between human T lymphotropic virus type I (HTLV-I) and hepatitis virus type B (HBV) infections, we compared both individual and geographical distributions of carriers of HTLV-I and HBV, and antibody positives to HBV in two ATL-endemic islands in Kyushu, Japan. The positive rates of antibodies to HTLV-I (anti-HTLV-I-Ab) in sera among healthy inhabitants older than 30 years of age were 27.5% (617/2,232) in Nakadohri, Goto Island and 24.0% (500/2,048) in Shimo-agata, Tsushima Island. The positive rates for surface antigen of hepatitis B virus (HBs-Ag) in sera among the same subjects were 6.4% and 2.5%, respectively. In Nakadohri, the age-adjusted positive rates of HBs-Ag and antibody to HBs-Ag (anti-HBs-Ab) in anti-HTLV-I-Ab positives (so-called HTLV-I carriers) differed little from those in negatives. In Shimo-agata, the geographical distribution of HBs-Ag positives (so-called HBV carriers) showed no positive association with that of HTLV-I carriers. These results did not support the positive correlations between HTLV-I and HBV infections among the general population in ATL-endemic areas in Japan.