Eighty-two patients, who were treated for post partum illness between 1946 and 1971, were identified and followed up. Diagnostically, the sample comprised unipolar depression (52%), bipolar disorder (18%), schizophrenia (16%), abnormal personality with depression (8%), organic disorder (2%), and obsessional state with depression and paranoid disorder (1% each). The overall prognosis was good, except for schizophrenia, in which more than 50% of patients had chronic disability. Further childbirth intensified, and caused deterioration of, the underlying schizophrenia process. Following an initial illness in the puerperium, the probability of a recurrent affective illness was 43% for unipolar and 66% for bipolar disorder. The risk of developing another post partum illness varied from 1 in 3 to 1 in 5 pregnancies. Five percent of the sample ultimately committed suicide, and the probable incidence of infanticide was 4%.