We describe four patients, two with Tourette's syndrome, one with the combination of idiopathic dystonia and essential-like tremor, and one with tardive dystonia, who noted marked exacerbation of their movement disorders after exposure to cocaine. These patients provide support for the hypothesis that dopaminergic preponderance plays an important role in the pathogenesis of certain hyperkinetic movement disorders. Cocaine should be regarded as an important cause or precipitant of hyperkinetic movement disorders.