Bromocriptine alters the motor behaviour of animals and improves the motor defect of parkinsonism. Changes in movement are accompanied by biochemical changes in the central nervous system, consistent with the idea that bromocriptine has a dopamine agonist action in the basal ganglia and also in the mesolimbic system and hypothalamus. The overall anti-parkinsonian effect of bromocriptine is similar to that of l-dopa alone or with benserazide (a decarboxylase inhibitor) when optimum doses are used, although individual patients may respond better to 1 drug than to the other.