The effect of combined pronator teres rerouting and flexor carpi ulnaris transfer on forearm rotation was prospectively studied by comparison of pre- and postoperative three-dimensional analysis of forearm range of motion in ten patients with cerebral palsy. One year postoperatively, surgery had improved maximal supination of the forearm in all patients by an average of 63°, but there was also a mean loss of 40° pronation. Forearm range of motion increased by a mean of 23°. The centre of the range of motion on average shifted 52° in the direction of supination. Based on these results of objective forearm range of motion analysis, we conclude that the common combination of pronator teres rerouting and flexor carpi ulnaris transfer in patients with cerebral palsy effectively facilitates active supination but impairs active pronation.