It has been hypothesized that the dietary sweetener aspartame (L-aspartyl-L-phenylalanine methyl ester) might promote seizures and this hypothesis has been argued in the published literature. The current manuscript reviews the biochemical, neurochemical and behavioral experiments that have been carried out in order to assess the hypothesis linking aspartame with seizure promotion. We conclude that convulsive seizures are not caused by orally administered aspartame in rodents or in primates, including humans. Early reports of seizure facilitation by aspartame in several rodent models were not confirmed by later and more careful experimentation. Proconvulsive effects were absent in humans and other mammals with epilepsy and those without epilepsy. Lack of convulsive liability was evident, even when doses many fold higher than those consumed in the human diet, were used in experimental paradigms. Studies of aspartame in absence seizures are not as complete as those in convulsive seizures, but available evidence in humans does not document an association between absence seizure incidence and aspartame usage.