Affective disorder is a serious and disabling illness which has a high suicide rate. Suicide is estimated as the eventual cause of death in 15 per cent of those given this diagnosis (4). Lithium carbonate has been convincingly shown to be an effective prophylactic against further attacks of depression (1, 3). Because suicide is such a common end in those with depressive illness, and per contra depressive illness is found in at least half of those dying by suicide (5, 2), the suicide rate may well go down once lithium is in general use. The reduction will depend on how many cases of suicide are recurrent depressives who might respond to lithium.