Benign sleep myoclonus in infancy is a distinctive but underdiagnosed disorder of quiet sleep, which according to our findings occurs from the first day of life up to age 3 years. Its main features are rhythmic myoclonic jerks when drowsy or asleep, which stop if the child is woken, and normal encephalograms during or after the episodes. 1 2 When all these features are present the diagnosis should be clear cut. The diagnosis may be difficult if the association with sleep is not noted and if no attempt is made to stop the “seizures” by waking the child. We report on15 patients in whom benign sleep myoclonus was initially mistaken for epilepsy.