Lines of evidence have been presented in further support of the continuum model of manic-depressive psychosis, in contrast to the more generally held bipolar model. In order to crystallize the evidence, the arguments previously presented, together with those now advanced, will be summarized so that the reader may evaluate the evidence independently. The bipolar model has as its chief support the evidence from behaviour changes which appear opposite in character—from retardation to over-activity. Secondly, the apparent bipolarity of mood from depression to mania has been repeatedly claimed. In defending the continuum model as an alternative, the first observation is not questioned but the second is. The positive points which support the continuum model, but are in conflict with the bipolar model, are as follows: 1. The transition which commonly occurs from depression to mania and vice versa , without normality intervening. 2. The addition of stress to a depressed patient which often results in mania. 3. The same forms of therapy prove effective both in mania and depression—this applies to ECT, anti-manic and anti-depressantmedication. 4. The triphasic character of the disorder with depression existing before, during and after manic episodes. 5. The existence of `mixed' states. 6. Psychophysiological and biochemical findings which present similarities of disturbance, with manics sometimes showing the greater disturbance. 7. Psychomotor performance which shows similar types of dysfunction but manics more impaired. 8. The relative frequency of mania and depression, both in population studies and in individual cycles. 9. The almost total absence of patients experiencing mania without depressive episodes. While the continuum model is nothing new to the psychoanalysts who `seem to agree that mania and depression are closely related' (Rosenfeld, 1963), it is undoubtedly time for those concerned with the application and the development of the physical therapies to question the assumptions of the bipolar model.