Most obstetric brachial plexus palsies are due to rupture of the upper roots in babies whose delivery was complicated by shoulder dystocia. If treated by early exploration and grafting, they have a favourable prognosis. We reviewed 36 babies who had had an obstetric brachial plexus palsy after a breech delivery and found that they had a different pattern of injury; 81% had avulsion of the upper roots. This injury cannot be treated satisfactorily by exploration and microsurgical grafting and carries a considerably worse prognosis for shoulder function.