A retrospective study of 92 patients admitted with mania, aged over 65 years of age, found that 26% had no prior history of affective illness; 30% had previously only experienced depression, and half of these had at least three episodes of depression before the first manic illness. Patients with a family history of affective disorders had a significantly earlier age of onset of illness. There was evidence of cerebral organic impairment in 24% of the patients, and this group had a significantly later age of onset of illness. Prognosis was good, with only 8% still in hospital at six months. Half of the patients were started on lithium prophylaxis, but this did not significantly alter the number of readmissions. A quarter of those started on lithium developed evidence of lithium toxicity.