Severe inhibition of haematopoiesis is a serious disease from the prognostic aspect. The authors evaluated a group of 26 patients of whom one survived for more than five years. The mean life span is 154 days. The most frequent cause of death are infectious complications, in particular septicaemia. Investigation of the aetiology of the disease was negative in 46% of the cases, in the remainder drugs were suspected most frequently, in particular antibiotics. It is very important to prevent the development of secondary inhibition of haematopoiesis, in particular by careful indication of myelotoxic drugs. In case of necessity, these drugs should be administered for a short time, in the lowest effective doses with check-ups of the haemogram. Hope for affected patients in future is transplantation of bone marrow and the early administration of antilymphocytic globulin.