At three centres, 21 women at high risk for puerperal psychosis were given prophylactic lithium carbonate late in the third trimester of pregnancy or immediately after delivery. Only two of the women had a recurrence of their psychotic illness while on prophylactic lithium. One woman given lithium during third trimester had an unexplained stillbirth. Although a larger sample in a carefully controlled study is still required, there now seems to be grounds for the use of prophylactic lithium immediately after delivery in women not breastfeeding who have previously suffered from either puerperal psychosis or bipolar disorder.