Analysis was made of serum anti-HTLV-I antibodies, virus-specific proteins in peripheral blood lymphocytes (PBL) and proviruses in lymphocyte DNA of a patient with adult T-cell leukemia (ATL), Kaposi's sarcoma, and chronic myelopathy. Using Western blot and PCR (with HIV-1 specific primers), it was shown that Kaposi's sarcoma was not linked to HIV infection. Western blot analysis of serum revealed antibodies against p19, p24 and Pr 53 of HTLV-I. Examination of proteins in fresh PBL by Western blot revealed a high level of HTLV-I specific protein expression. Southern blot analysis of the patient's DNA revealed two different sites for HTLV-I provirus integration.