A nationwide survey of patients in Japan with spinocerebellar degenerations (SCD), including SDS and SND, was conducted from 1988 to 1989. The survey consisted of two parts. The first revealed that the estimated total number of patients with SCD in Japan was 5,050 (range: 4,100-6,000) with an estimated prevalence of 4.53 per 100,000 in 1987. The second part investigated the neurological and functional status of patients with SCD. The percentages of those belonging to each subtype of SCD were: OPCA; 34.4%, LCCA; 15.2%, MHCA; 12.6%, HHCA; 7.5%, SDS; 7.0%, HSP; 3.9%, DRPLA; 2.5%, FA; 2.4%, MJD; 2.0% and SND; 1.5%. Compared with European epidemiological studies Japan had a higher proportion of non-hereditary types of SCD. Various clinical features of SCD subtypes were compared grouped by pathological lesion and heredity. HHCA and LCCA: cerebellar ataxia predominated in all stages, and neurological signs other than cerebellar ataxia were rare. MHCA, DRPLA and MJD: in the early phase ataxia was the most common symptom in MHCA, the AC form of DRPLA and MJD, but ataxia was less common and chorea or epilepsy were often observed in ME and PH forms of DRPLA. Other frequently observed clinical features were parkinsonian rigidity in MHCA, abnormal movements and posture in DRPLA and MJD, and disturbances of eye movements in MHCA, the AC form of DRPLA and MJD. OPCA, SDS and SND: dominant clinical features were cerebellar ataxia in OPCA, autonomic disturbance in SDS, and parkinsonian rigidity in SND. FA and HSP: both were rare in Japan. Clinical features related to supra-supinal lesions were frequently observed in FA. Functional status of SCD: the severity of illness was significantly associated with the level of independence in each item of ADL. Activities not requiring dynamic balance were performed independently for a longer period than those requiring dynamic balance. Among SCD subtypes, functional prognosis was poorest in non-hereditary, multi-systemic types (OPCA, SDS and SND) followed by hereditary multi-systemic types (MHCA, DRPLA and MJD), and better in spinal types (FA and HSP) and cerebellar types (HHCA and LCCA).