We analyzed neuropathologic features of 23 Japanese patients with sporadic Creutzfeldt-Jakob disease (sCJD) by means of prion protein (PrP) immunolabeling associated with codon 129 polymorphism of the PrP gene and western blot analysis of protease-resistant PrP (PrP type). Clinical features, particularly age at onset, disease duration, periodic synchronous discharge and presence of myoclonus, were also analyzed. This study included 11 cases of subacute spongiform encephalopathy (SSE), 10 cases of panencephalopathic (PE)-type sCJD and two cases of thalamic-type sCJD, classified according to cerebral pathology findings. According to PrP gene polymorphism and PrP type, 18 cases were classified as MM1-type, two as MV1-type, two as MM2-type and one as MM1 + 2-type sCJD. SSE and PE-type sCJD showed similar clinical features, with the exception of disease duration, codon 129 polymorphism and PrP type. Thalamic-type sCJD showed different clinical features and PrP type. We suggest that SSE and PE-type sCJD comprise the sCJD subtype and that PE-type sCJD is a prolonged pathologic phenotype of SSE. When we compare our results with those from a series of Caucasian sCJD patients, the percentages of codon 129 polymorphisms differed, as did classification based on PrP gene polymorphism and PrP type; our series included many PE-type sCJD cases and disease duration was relatively long and MM2-type cases showed clinicopathologic variability.