Metabolic depression in the contralateral cerebellar hemisphere caused by a supratentorial lesion is called crossed cerebellar diaschisis (CCD). In order to investigate diaschisis based on the location and extension of lesions, time course and prognosis, 31 patients with putaminal hemorrhage were examined by the Xe-133 clearance method (67 studies in all). They consisted of 20 males and 11 females, from 40 to 77 years old (mean: 57.1 +/- 8.9). Small hematomas (mean volume: 16.1 +/- 8.4 ml) in 18 patients were treated nonsurgically, whereas medium and large hematomas (mean volume: 57.5 +/- 29.9 ml) in 13 patients were treated by craniotomy for evacuation. rCBF was measured using a BI 1400 rCBF Analyzer (Valmet, Denmark), and CCD was considered positive when the percentage difference in cerebellar blood flow was 10.1% (mean + 2SD) greater than obtained in 21 normal controls. CCD was observed in 10 patients (55.6%) in the non-surgical group and in 9 patients (69.2%) in the surgical group. In the non-surgical group, CCD was positive in 5 of the 7 cases (71.4%) involving the posterior limb of the internal capsule and in 7 of the 11 cases (63.6%) involving the corona radiata. The surgical group was divided into three types based on the time course of CCD after surgery, i.e., type A: persistent CCD found two months later, type B: postoperative CCD had resolved two months later, and type C: no CCD observed after surgery. Mean hematoma volume was significantly greater in type A (79.0 +/- 19.8 ml) than in type B (44.6 +/- 8.5 ml) or type C (30.7 +/- 3.7 ml) (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)