PURPOSE: To compare the preoperative and postoperative pattern of firing of the flexor carpi ulnaris (FCU) in a grasp and release functional activity for children treated with an FCU to extensor carpi radialis brevis tendon transfer for wrist flexion deformity associated with spastic hemiplegia from cerebral palsy. METHODS: Seven children, evaluated by a preoperative EMG video analysis and treated with an FCU to extensor carpi radialis brevis transfer, had a follow-up postoperative EMG/video motion laboratory analysis at an average follow-up of 3.5 years (range, 1.0-6.8 years). Each preoperative and postoperative EMG/video was reviewed for the task of lifting heavy cans, as described by Jebson et al. The EMG activity of the FCU was described as active or relaxed during grasp and during release. RESULTS: Preoperatively, the most common pattern was to activate the FCU during grasp and to relax the FCU during release (4 patients). Postoperatively, 6 patients activated the FCU during grasp and relaxed the FCU during release; 1 patient activated the FCU during both grasp and release. CONCLUSIONS: Of the 7 patients studied, the FCU changed phase from preoperative to postoperative in only 1. This study concludes that most commonly the FCU does not predictably change phase when transferred from a position of wrist flexion to wrist extension. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.