Abstract Response to prophylactic lithium was studied in relation to clinical and psychological characteristics in a large series of patients with recurrent affective disorders. The findings were that bipolar patients with a family history of mania or depression had more favourable responses than those with no family history of affective disorders. Unipolar patients with more endogenous illnesses and those with pure familial depressive disease had more favourable responses than those with less endogenous illnesses and those with sporadic and depression spectrum diseases. Good responders showed generally less personality disturbance on a variety of measures than fair-to-poor responders. Response to lithium over 6 months in unipolar illness and over the first year in bipolar illness was strongly associated with long-term response.