Between 1974 and July 1987 the diagnosis of severe aplastic anaemia (SAA) was confirmed in 82 patients. Overall actuarial survival was 57% at 7 yr. Four patients recovered while receiving conventional therapy, and four died before treatment with antithymocyte globulin (ATG) or bone marrow transplantation (BMT) could be initiated. Nineteen patients (median age 19.6 yr) were treated with allogeneic BMT (11 as initial therapy, eight after ATG). Incidence of acute and chronic graft versus host disease was high, occurring in 14/16 and 4/11 patients at risk, respectively. Survival of BMT patients (18/19 transfused) was 32% at 7 yr. Of 63 patients treated with ATG, survival was 63% at 7 yr but decreased to 43% at 11 yr. The 2.5 yr survival following ATG was influenced by pretreatment disease severity (defined by percentage reticulocytes, granulocyte and platelet counts), age and--in patients under 45 yr of age--by sex. However, pretreatment disease severity was less in patients aged between 20 and 45 yr and in females. Concomitant androgen therapy, animal source of ATG, interval diagnosis--ATG (which was in general rather short) and aetiology did not influence survival. Thirty-four patients became transfusion independent for up to 26 months after ATG. A gradual increase in granulocyte and platelet counts could be observed over a period of many years, and 26 patients recovered to show a normal haemoglobin level, granulocytes greater than or equal to 1.0 X 10(9)/l and platelets greater than or equal to 100 X 10(9)/l). Late complications (paroxysmal nocturnal haemoglobinuria, myelodysplastic syndrome/acute leukaemia, hepatocellular carcinoma) were observed in nine patients who survived with autologous marrow function. Five died within 12 yr of initial therapy.(ABSTRACT TRUNCATED AT 250 WORDS)