Introduction: Botulinum toxin A (Btx-A) blocks neurotransmission at the neuromuscular junction by preventing acetylcholine release from the presynaptic motor nerve terminal. Btx-A has been used to manage spasticity associated with cerebral palsy in the last several decades. However, the functional recovery of the injected muscles following toxin injections remains unclear. An improved understanding of the time course of recovery of the targeted muscle would provide information necessary to standardize the techniques of Btx-A injection in pediatric cerebral palsy patients. Material and methods: Btx-A was injected into the left gastrocnemius of 29 1-month old Sprague-Dawley rats at the dosage of 6 units/kg. The same volume of saline was injected into the right gastrocnemius to serve as a control. Muscle mass, motor evoked action potentials (latency, amplitude and area under the curve) and muscle force generation were evaluated at 3 days, 7 days, 14 days, 1 months, 2 months and 3 months after injection. (n=4-5 at each time point). Results: Muscle mass was reduced by 31.5% of the contralateral side within 2 weeks, and at 3 months was still reduced 27.1%. Latency was delayed to 144.9% at 3 days and recovered to 112.3% at 3 months. Amplitude and area under the curve decreased to approximately 30% at 3 days, then gradually recovered to 80% at 3 months. Single twitch was decreased to 12.3% at 1 week, but recovered to 86.3% at 3 months; tetanus decreased to 24.4% at 3 days, then gradually recovered to 91.5% at 3 months. Discussion: The motor evoked action potentials and muscle force generation recovered faster during the first month than the second and third month. Btx-A at dosage of 6 units/kg could induce substantial muscle atrophy but reversible muscle weakness within 3 months following toxin injection. The recovery of motor action potentials and muscle force generation indicates that most neuromuscular junctions have been re-established functionally.