This study compared the effects of low and high doses of botulinum toxin A (BTX-A) to improve upper extremity function. Thirty-nine children (22 males, 17 females) with a mean age of 6 years 2 months (SD 2y 9mo) diagnosed with spastic hemiplegia or triplegia were enrolled into this double-blind, randomized controlled trial. The high-dose group received BTX-A in the following doses: biceps 2U/kg, brachioradialis 1.5U/kg, common flexor origin 3U/kg, pronator teres 1.5U/kg, and adductor/opponens pollicis 0.6U/kg to a maximum of 20U. The low-dose group received 50% of this dosage. Outcomes were measured at baseline and at 1 and 3 months after injection, and results were analyzed with a repeated-measures analysis of variance. There was no significant difference between the low-dose and high-dose groups in upper extremity function over the 3-month period as measured by the Quality of Upper Extremity Skills Test (F[1,37] = 0.18, p = 0.68). There was no difference between the groups in the Pediatric Evaluation of Disability Inventory Self Care Domain (F[1,37] = 0.05, p = 0.83). Although grip strength decreased over the 3-month period, there was no difference between groups (F[1,32] = 0.45, p = 0.51). These findings indicate that there is no difference in hand and arm function between a low dose and a high dose of BTX-A at 1 and 3 months after injection. This information can be used to guide dosage of BTX-A for the management of upper extremity spasticity in children. (Contains 5 tables and 1 figure.)