We report here four unrelated DOPA-responsive dystonia pedigrees in which loss-of-function GCH1 mutations (two splice-site mutations and two missense mutations, confirmed to be pathogenic by metabolic or CSF studies) were found in individuals, asymptomatic for DOPA-responsive dystonia during childhood, who developed adult-onset parkinsonism. The gene discussed is GCH1; the disease is Dystonia.