Of twelve patients with malignant histiocytosis admitted between 1974 and 1987, clinical symptoms, diagnostic procedures and the course of the disease were retrospectively evaluated. Predominant findings at physical examination were fever (11/12), splenomegaly (12/12), hepatomegaly (8/12), and lymphadenopathy (8/12). Laboratory findings included anaemia, leukocytopenia, thrombocytopenia, high lactate dehydrogenase, and jaundice. Positive diagnostic procedures included biopsies or aspirates of bone marrow (11/12), spleen (6/10), liver (7/9), lymph node (4/4), skin (1/2), lung (1/1) and blood (2/12). In seven patients treated with combination chemotherapy an average survival of 540 days was observed, while two long-term disease-free survivals were accomplished.