Milacemide, 2-N-pentylaminoacetamide, a glycine prodrug, which readily crosses the blood-brain barrier, has been tested for antiepileptic efficacy and tolerability in 30 patients compared in a double-blind design with 30 patients treated with placebo. All patients continued to receive, without alteration, their previous partly effective medication. All patients presented an average of at least 10 seizures a month during the 6 months preceding the trial with no more than 50% fluctuation. The ratio of seizure frequency in the trial period over the seizure frequency in the baseline period (RSF) was calculated. In the milacemide group, 9 of 29 patients had an RSF less than 0.7 as opposed to 2 of 29 in the placebo group. Although no firm proof of therapeutic efficacy, this and the dramatic improvement of a patient with myoclonus epilepsy indicates that further studies are warranted. This opinion is strengthened if one considers the subgroup of patients aged less than or equal to 25 years in which a statistically significant reduction in seizure frequency was observed with milacemide treatment. The drug was well tolerated.