Aims: In this study the aim was to evaluate the effect of botulinum toxin A (BoNT-A) treatment on muscle tone, contracture development and gait pattern in young children with cerebral palsy (CP). Method: Fifteen children with spastic CP (mean age = 16 months) were included in a randomized control study. All received a daily stretching programme and children in the BoNT-A group additionally received two injections, 6 months apart in the gastrocnemius muscle. Outcomes were assessed at baseline, and after 1 and 3.5 years. A 3D gait-analysis was performed at 5 years of age. Results: Plantarflexor muscle tone in the BoNT-A group was significantly reduced after 3.5 years, while the muscle tone at the ankle and knee in the control group remained unchanged. The change-score in knee-flexion muscle tone between the groups was significantly different after 3.5 years. The knee joint ROM was significantly increased at 1 year in the BoNT-A group but reduced at the knee and ankle joints in the control group after 3.5 years. No group differences were found for gait analysis, GMFM-66 or PEDI. Conclusion: Early treatment of BoNT-A in children with spastic CP may decrease muscle tone and decelerate contracture development after 3.5 years. The effect on gait development remains inconclusive.