Autosomal recessive early-onset parkinsonism with diurnal fluctuation (AR-EPDF, syn. autosomal recessive juvenile parkinsonism, PARK2) is one of the hereditary parkinsonian syndromes. We examined subjects consisting of 43 patients from 22 families with AR-EPDF. The clinical features were relatively homogeneous, including the average age at onset of 26.1 years, beginning with dystonic gait disturbance, diurnal fluctuation of the symptoms (sleep benefit) unrelated to medication, dystonia (mainly foot dystonia), hyperactive tendon reflex, remarkable effect of levodopa and other antiparkinsonism drugs, susceptibility to dopa-induced dyskinesia, mild autonomic symptoms, absence of dementia, and slow progression of disease. Some patients had hysteric character or psychic symptoms provoked by medication. Pathologic study revealed neuronal loss in the substantia nigra pars compacta and locus coeruleus without Lewy body formation. We performed extensive molecular genetic analysis of the parkin gene in 16 families to identify a total of six different deletional mutations. In AR-EPDF loss of newly discovered 'Parkin' protein is responsible for selective degeneration of the pigmented neurons in the substantia nigra and locus coeruleus. Compared with autosomal dominant Parkinson's disease, AR-EPDF appears to be more prevalent and present in several ethnic groups.