In this study, we compared the long-term efficacy and tolerability of two dosage regimens of the potent botulinum toxin type A (BoNT-A; Dysport; Ipsen Ltd, Slough, UK) in children with cerebral palsy (CP) and lower-limb spasticity. Children aged 1 to 8 years with diplegic CP who were able to walk (aided or unaided) were randomized (1:1) to 30 LD(50) units/kg total body weight of BoNT-A (injected into gastrocnemius muscles) every 4 months or once yearly for 2 years in this multicentre, assessor-blinded, parallel-group study. In the 4-monthly group (n=110, 39 males, 71 females), mean age was 3 years 8 months (SD 1 y 6 mo, range 1-8 y). In the yearly group (n=104, 47 males, 57 females), mean age was 4 years 4 months (SD 1 y 6 mo, range 2-8 y). Both treatment groups had similar baseline Gross Motor Function Measure scores. At month 28 (primary endpoint; intention-to-treat group), median maximum passive ankle dorsiflexion was 12.00 degrees in the 4-monthly and 11.00 degrees in the yearly group. Between-group difference of 1.67 degrees was not statistically significant (p=0.055). Other efficacy endpoints showed no significant difference between the regimens. The results of the study do not allow a clear conclusion of the preferred injection regimen.