Introduction Pneumocystis carinii pneumonia is an infection affecting primarily premature and weak infants. It is characterized by progressive dyspnea, cyanosis, tachypnea, and tachycardia. There are no or only slight signs upon physical examination of the chest, as opposed to a radiological picture showing progressive opacities in the lungs, fever, tendency to leukocytosis, lack of response to any therapy, and a usually fatal outcome, death being the result of respiratory failure. Pathologically it is characterized by infiltration of the alveolar septa by mononuclear cells, mostly plasma cells, and the presence of numerous small round bodies, Pneumocystis carinii, within the alveolar spaces. The causal agent is Pneumocystis carinii, thought to be a protozoan parasite. Already well known as a pediatric problem, Pneumocystis carinii pneumonia in adults is rare, and has until now been recorded as a secondary finding in patients suffering from malignant diseases, mainly of the lymphoreticular system or leukemia. We