The retrospective study of adults who develop depression has not established childhood separation experiences as predisposing to depression, nor has the work on psychologic causes prior to onset of adult depression produced a clear statement as to the cause of depression. Prospective studies have the advantage of identifying cases more accurately. Grief, following the loss of close relative, can be studied prospectively as a possible cause of depression. Attention should focus on the factors which impinge upon the bereaved and his reactions to these after the loss. Such studies, heretofore largely neglected, promise a better understanding of the causes of depression than previous retrospective studies. More attention to the therapy of the bereavement period could lead to a reduction in the incidence of depression.