Owing to the lack of instruments specifically constructed to study emotional and affective disorders of stroke patients, the nature of post-stroke depression (PSD) remains controversial. With this in mind, the authors constructed a new scale, the Post-Stroke Depression Scale (PSDS) which takes into account a series of symptoms and problems commonly observed in depressed stroke patients. The PSDS and the Hamilton Depression Rating Scale (HDS) were administered to a group of 124 patients, who had been classified, on the basis of DSM III-R diagnostic criteria, in the following categories: No depression (n = 32); Minor PSD (n = 47); Major PSD (n = 45). Scores obtained by these stroke patients on the PSDS and on the HDS were compared to those obtained on the same scales by 17 psychiatric patients also classified as major depression on the basis of DSM III-R diagnostic criteria. An analysis of the symptomatological profiles clearly showed that: (1) a continuum exists between the so-called "major" and "minor" forms of PSD; (2) in both groups of depressed stroke patients the depressive symptomatology seems due to the psychological reaction to the devastating consequences of stroke, since the motivated aspects of depression prevailed in depressed stroke patients, whereas the (biologically determined) unmotivated aspects prevailed in patients with a functional form of major depression; and (3) in stroke patients a DSM III-based diagnosis of major PSD could be in part inflated by symptoms (such as apathy and vegetative disorders) that are typical of major depression in a patient free from brain damage, but that could be due to the brain lesion per se in a stroke patient.