This study evaluated the sleep–wake pattern, plasma melatonin levels and the urinary excretion of its metabolite, 6‐sulphatoxy‐melatonin among children with severe epileptic disorders, before and after a therapeutic trial with melatonin. Ten paediatric patients, suffering from severe epileptic disorders, were selected and given a nightly dose of 3 mg of a placebo, for 1 wk; for the next 3 months, the placebo was replaced with a nightly dose of 3 mg of melatonin. At the end of each treatment period, the urinary excretion of 6‐sulphatoxy‐melatonin (for the intervals 09.00 – 21:00 hr or 21:00–09:00 hr) and plasma levels of melatonin (recorded at 01:00, 05:00, 09:00, 13:00, 17:00 and 21:00 hr) were recorded, over a period of 24 hr; an actigraph record was also kept. Sleep efficiency among patients who received melatonin was significantly higher than among those given the placebo, with fewer night‐time awakenings. Periodic plasma melatonin levels were regained and a better control gained of convulsive episodes, in that the number of seizures decreased. We conclude that melatonin is a good regulator of the sleep–wake cycle for paediatric patients suffering from severe epilepsy, moreover, it to a better control of convulsive episodes.