This study used a repeated measures design to assess the effect of an eight-week repetitive passive movement (RPM) intervention on lower extremity muscle tone and function in children with cerebral palsy (CP). Eighteen children (aged 9.5 [plus or minus] 2.1 years) with spastic CP were randomly assigned to a knee RPM intervention condition of 3 times a week for 8 weeks or a control condition. The 8 weeks were followed by 4 weeks of washout period, after which the participants were crossed over to the other group. In the RPM condition, each subject's knees were intervened with continuous passive motion device (at a velocity of 15[degrees]/s) for 20 min. The subjects were evaluated via variables measuring range-of-motion, muscle tone, and ambulatory function before, after, 1 day after, and 3 days after each intervention. Repeated-measures statistical analyses found significant differences between condition variable on active range-of-motion of the knee (AROM, increased), relaxation index (RI, increased), Modified Ashworth Scale (MAS, decreased), timed up-and-go (TUG, decreased), 6-min walk test (6MWT, increased); and significant differences among time variable including RI, MAS, and 6MWT. No difference was found in passive range-of-motion measurements. Repetitive passive movement reduced lower extremity spastic hypertonia in children with cerebral palsy, and it also improved ambulatory function in terms of walking speed. Effects of this treatment protocol on ambulation lasted up to 3 days post intervention. Findings of this study provide clinicians and patients an alternative, effective and efficient strategy for spastic control and ambulatory improvement. (Contains 1 table and 3 figures.)