This study explored the safety and efficacy of synthetic melatonin in the treatment of sleep problems in 20 children with developmental disabilities, in a randomized, double-blind, placebo-controlled 6-week trial of melatonin versus placebo. All but 2 children fell asleep more quickly when receiving melatonin than placebo. Overall, the greater the sleep latency (time to fall asleep) was at baseline or when receiving placebo, the more pronounced was the decrease in sleep latency with melatonin. The effect of melatonin on sleep latency was significant (P < .05). The duration of sleep while receiving melatonin was significantly greater than baseline (P < .007) but was not significantly different from placebo, and no difference in the number of awakenings was noted. No side effects were reported. Eleven of 18 parents (61%) correctly identified the weeks their child received melatonin. This study suggests that synthetic melatonin reduces sleep latency in children with developmental disabilities.