We recently described an infantile onset spinocerebellar ataxia (IOSCA) in 19 Finnish patients. The classification of hereditary ataxias of unknown etiology is difficult because of the heterogeneity of these diseases. The clinical course of IOSCA is homogeneous. Ataxia, muscle hypotonia, athetosis, and loss of deep tendon reflexes in the legs appeared around the age of 1 year. Ophthalmoplegia and deafness were found by school-age, and sensory axonal neuropathy and optic atrophy by adolescence. An acute crisis with epilepsy was a late manifestation. The female patients had hypogonadism. In order to define the type of hypogonadism and to exclude other endocrine defects we measured serum concentrations of SHBG, DHEAS, prolactine, testosterone/estradiol, FSH and LH in postpubertal patients. ACTH, hCG and GnRH tests were performed to both pre- and postpubertal patients. Growth was analysed, and the brain and pituitary region were examined with magnetic resonance imaging (MRI). The estradiol values were low and FSH and LH values were high in the female patients, which indicates that the hypogonadism was of the hypergonadotropic type. The growth of the female patients was steady without a significant pubertal growth acceleration. The growth and pubertal development of the male patients were normal. The adrenal cortical and thyroidea functions were normal in all patients.