We studied the effect of apomorphine, a dopamine receptor agonist, on epileptic photosensitivity in 7 patients with progressive myoclonus epilepsy (PME). Specific diagnoses included Baltic PME (Unverricht-Lundborg disease), Lafora disease, Kufs' disease, juvenile neuroaxonal dystrophy, and action myoclonus-renal failure syndrome; 2 patients had PME of uncertain etiology. Apomorphine blocked the epileptic photosensitivity in all patients and also reduced intention myoclonus in a patient with Baltic PME. There is a common deficit of dopaminergic inhibitory neurotransmission at the level of the striate cortex in patients with PME, regardless of the nature of the specific underlying neuropathologic process.