The reactive or virus-associated haemophagocytic syndrome (RHS) has been described in association with several different infections and is regarded as clinically and pathologically distinct from malignant histiocytosis. A case is described of this syndrome in a 30-year-old HIV-antibody positive homosexual male who presented with fever, pancytopenia, lymphadenopathy, and massive splenomegaly. The fever and haematological abnormalities resolved following splenectomy, and the patient remains well after 12 months. Prominent histiocytic haemophagocytosis was seen in both the spleen and an abdominal lymph node. Exhaustive tests failed to demonstrate any infectious agent other than human immunodeficiency virus, indicating this to be a case of this syndrome occurring in association with HIV infection.