To confirm and differentiate between human T-cell lymphotropic virus type I (HTLV-I) and HTLV-II infections, we analyzed by polymerase chain reaction (PCR) samples of peripheral blood lymphocytes from 98 individuals seropositive for HTLV-I/II using pol (SK110/111) and tax (SK43/44) consensus primer pairs. A total of 96 samples (97.9%) were positive by the tax generic probe, while 95 were typed by the HTLV-I and HTLV-II pol probes. The three pol-negative samples were successfully amplified and typed by nested PCR with primers internal to SK110 and SK111. Results of PCR with a lysate of leukocyte nuclei obtained by whole blood lysis were comparable to those obtained with peripheral blood lymphocytes from 16 HTLV-seropositive subjects.