In a controlled study, 26 severely disabled cerebralpalsied children were given diazepam in oral doses or matching placebos, alternated every two or four weeks for a total period which varied from 5 weeks to 38 weeks, averaging five months. Results compiled from detailed semimonthly evaluations by therapists and nurses disclosed that ten children achieved excellent muscle relaxation during diazepam therapy (but no improvement with placebo) which accelerated progress in training in some, and facilitated management of all. In 16 children, improvement differences between drug and placebo trials were not significant. Athetoid patients responded better than spastics. Diazepam eliminated or suppressed the startle reflex in all children; it had no apparent effect on appetite, chewing, swallowing, drooling, or bed wetting. Side effects of lethargy were negligible, once optimal therapeutic doses, averaging 21/2 mg three times a day, were attained.