Serum ferritin has been analysed and bone marrow haemosiderin evaluated in 306 patients with malignancies, mostly lymphomas, and in 46 healthy controls. Also haemoglobin, serum iron, transferrin and liver enzymes were analysed simultaneously. 60% of the patients had serum ferritin above normal values and 20% had values above 1000 micrograms/l. There was a good correlation between serum ferritin and bone marrow iron both in the patients and in the controls, r = 0.67 and r = 0.77, respectively. There was a negative correlation between serum ferritin and haemoglobin concentration in the patients and a positive correlation in the controls. In patients with Hodgkin's disease serum ferritin was related to the stage of the disease.