We present 7 children with obstetric brachial plexus palsy treated by transferring two motor fascicles out of the ulnar nerve to the biceps nerve. Three were male, and 4 were female. The left-side brachial plexus was affected in 4 patients, and the right side in 3 patients. All children had vaginal delivery; two of them presented with shoulder dystocia. The average birth weight was 4300 g (range, 3620-5500 g). Average age at time of operation was 16 months (range, 11-24 months). The indication for the operation was absent active elbow flexion with active shoulder abduction against gravity in 4 cases, and no biceps function and bad shoulder function in 3 cases. Oberlin's ulnar nerve transfer was done in 4 cases without brachial plexus exploration in those children with good shoulder function, and exploration of the brachial plexus was performed in the other 3 cases with bad shoulder function. The average follow-up was 19 months (range, 13-30 months). Five children had biceps muscle >or=M(3) with active elbow flexion against gravity, and 2 children had biceps muscle <M(3). We recommend Oberlin's ulnar nerve transfer for upper-type obstetric brachial plexus palsy in 1). breech delivery with avulsion of C5 and C6 nerve roots,) late presentation with good recovery of shoulder function, and 3). neuroma-in-continuity of the upper trunk with intraoperative good nerve conduction for the shoulder muscles, the same as preoperative good shoulder function but with no biceps action. Copyright 2004 Wiley-Liss, Inc.