The signs, symptoms and courses of 64 cases of "primary" haematoma of the basal ganglia have been retrospectively studied, and the main clinical data have been analyzed in relation to the location and extent of the bleeding. Onset with hemiplegia, accompanied or not by impaired consciousness, was more frequent with intermediate and lateral haematomas than with medial haematomas (p less than 0.001). Among patients with initial hemiplegia, impaired consciousness was more frequent with intermediate and medial haematomas than with lateral haematomas (p less than 0.005). At a later stage, patients with intermediate and lateral haematomas more often went into deep coma than those with medial haematomas (p less than 0.01). There were no statistically significant differences between the three anatomical groups with regard to frequency of other signs and symptoms or duration of the disease before death occurred.