Piracetam is an effective symptomatic treatment for some types of myoclonus in adults. To survey the efficacy and safety of piracetam in pediatric opsoclonus-myoclonus, we conducted an open, randomized, two-period, dose-ranging, double-blind, crossover, clinical trial of five children comparing the antimyoclonic properties of oral piracetam to placebo. We devised and validated a new rating scale, specifically for pediatric opsoclonus-myoclonus. Two parents while blinded were able to identify the active phase by improvement in behavior, but another thought the behavior was worse. None of the patients showed improvement in myoclonus. The adult-equivalent dose of piracetam used in this study, which is threefold higher than that used in previous pediatric studies, was well tolerated and safe. We found our rating scale to be a reliable and useful tool for future studies of opsoclonus-myoclonus in children.