The purpose of this longitudinal study was to identify changes in ERG responses associated with vigabatrin treatment. We accomplished this by recording longitudinally ERGs in children before and during vigabatrin treatment and comparing results between children on vigabatrin monotherapy and those taking additional anticonvulsive medications. Thirty-three children on vigabatrin therapy were tested; the duration between visits was approximately 6 months. Thirteen children were assessed initially before starting vigabatrin therapy and seven were assessed soon after (age range 1.5–126 months, median 6 months). The remaining 13 patients were already on vigabatrin at the time of initial visit (age range 6.5–180 months, median 16 months). ERGs were tested using the standard protocol established by the International Society for Clinical Electrophysiology of Vision, with Burian-Allen bipolar contact-lens electrodes. In addition to standard responses we recorded photopic oscillatory potentials (OPs). All 33 patients were tested longitudinally on at least two occasions and 11 were tested on three occasions. For children whose only anticonvulsive drug was vigabatrin there was a significant curvature (quadratic function, p<0.05) of="" the="" predicted="" cone="" b-wave="" amplitude="" with="" time;="" exhibited="" as="" increase="" in="" b-wave="" amplitude="" followed="" by="" subsequent="" decrease.="" descriptive="" data="" demonstrated="" the="" same="" pattern="" in="" the="" group="" taking="" anticonvulsive="" medications="" in="" addition="" to="" vigabatrin.="" in="" most="" children="" the="" flicker="" amplitude="" declined="" between="" 6="" months="" and="" 1="" year="" of="" vigabatrin="" treatment.="" our="" data="" demonstrated="" that="" rod="" responses,="" which="" may="" be="" abnormal="" before="" initiation="" of="" vigabatrin,="" did="" not="" change="" substantially="" with="" vigabatrin="">