A double-blind, crossover technique was devised to assess the value of chronic cerebellar stimulation in children with cerebral palsy. Cerebellar stimulators were implanted in eight children and adolescents with cerebral palsy. The external transmitter was changed monthly during each of the first 3 months and was set to be functional or placebo by random assignment. Objective assessment by physical, occupational, and speech therapists as well as by a neurologist failed to document significant improvement in any of the participants. Some children became less spastic and developed increased mental alertness and improved clarity of speech. However, these improvements occurred during placebo periods as often as with stimulation.