In the June 13 issue ofThe Journal, M. Robert-Guroff et al1reported antibody prevalences of 9% for human T-cell lymphotropic virus (HTLV) type I, 18% for HTLV-II, and 41% for HTLV-III in drug abusers in New York. Of concern is the known association of HTLV-I and adult T-cell leukemia (ATL), raising the possibility that this report of serological findings may be the forewarning of serious clinical events yet to come. Although HTLV-I is endemic in some areas of Japan, the Caribbean, and Africa, both HTLV-I infection and ATL are rare in the United States.2,3In Kyushu, an endemic area in Japan, a recent study revealed that 100% of 18 patients with ATL had HTLV-I antibodies, compared with 16% HTLV-I seropositivity in 604 apparently healthy adults.2Other studies of healthy populations in Japan indicate that high rates of HTLV-I infection are restricted geographically, with prevalences ranging from