A married couple who developed adult T-cell leukemia (ATL) is described. The husband presented with acute ATL and died soon after admission in spite of aggressive chemotherapy, and his wife, who is diagnosed as smoldering ATL, has been followed in the out-patient clinic. The couple had serum antibodies against human T-cell leukemia virus type I (HTLV-I) and the monoclonal integration of HTLV-I proviral DNA in their lymphocytes. The patients described represent the first reported example of ATL in a married couple.