As far as iatrogenic damage to haematopoesis in old-aged patients is concerned, diagnostic methods present little danger. However, a staging-laparotomy in malignant lymphomas is contraindicated. Significant are late-initiated examinations due to uncontemplated haematological illnesses, especially erythropoiesis. Polymorbidity often leads to medicinal polypragmasy especially when several organ specialists are at work and the local practitioner is not carrying out the treatment alone. The results are agranulocytosis and aplastic anaemia. An intensified hemorrhagic diathesis can occur with old age through damage to the functioning of the thrombocytes. An increased preparedness for thrombosis in old age necessitates a fortified thrombosis prophylaxis. Anticoagulants should be used with extreme precaution. In the treatment of haematoblastosis aggressive chemotherapy can be replaced by symptomatic methods with increased old age.