Previous experimental studies have shown that the simultaneous administration of gamma-aminobutyric acid (GABA) and phosphatidylserine (PS) can exert an anticonvulsant activity in different seizure models; moreover, a preliminary trial showed some effect of the association GABA-PS in patients with absence seizures. The aim of this study was to investigate the antiepileptic properties of GABA-PS in the model of human photosensitivity. Nine patients with epilepsy associated with an EEG pattern of photoconvulsive response at intermittent photic stimulation entered a 3-day study. The photosensitivity range (PSR) was determined at hourly intervals both in basal conditions and after the administration of a single oral dose of GABA (3000 mg) and PS (600 or 1200 mg). The administration of GABA-PS was not associated with any systematic changes of PSR, nor with any significant differences of time course profiles on each daily session. No correlation was found between PSR percent deviations from baseline and GABA serum levels. These results indicate that a single acute administration of GABA-PS has no effect in the human photosensitivity model, and suggest that the efficacy of GABA-PS in human epilepsy, as shown by a preliminary investigation, may possibly require chronic administration.