Visual (V), somatosensory (S) and brainstem auditory (BA) evoked potentials (EPs) were determined in 22 epileptic patients, mostly with partial seizures, who received add-on treatment with vigabatrin (1–3 g/day, stratified according to body weight) and placebo, each given for 7 weeks according to a double-blind, randomized cross-over design. At pretreatment assessment, BAEPs and SEPs were found to be within normal limits in most of the patients tested, while for VEPs several abnormal responses were found, including a marked prolongation of P100 latency values in the majority of cases. None of the EP parameters examined was significantly influenced by vigabatrin treatment. These results support the evidence that enhancement of GABA-ergic transmission does not substantially affect the functional state of afferent sensory pathways as assessed by EP analysis. The significance of these findings with respect to the safety of vigabatrin therapy is discusse