Obstetric brachial plexus palsy has two distinct categories: (1) early obstetric brachial plexus palsy (or obstetric brachial plexus palsy in an infant) and (2) late obstetric brachial plexus palsy with deformity (or obstetric brachial plexus palsy in a child). Both early and late obstetric brachial plexus palsy lack a uniform evaluation system, and this makes correlation between them difficult. Clinical evaluation of obstetric brachial plexus palsy in infants is difficult, but in children it is easier. Here, we utilized a new evaluation system, called “Score of 10,” to evaluate 121 late obstetric brachial plexus palsy patients based on patient's functional ability and surgeon's feasibility for reconstruction. “Score of 10” is a method combining the Erb and Klumpke scores. The Erb score gives points for upper plexus functions including shoulder abduction, shoulder external rotation, elbow flexion, elbow extension, forearm supination, forearm pronation, and trumpet sign. The Klumpke score gives points for lower plexus functions including wrist extension, wrist flexion, metacarpophalangeal joint extension, interphalangeal joint extension, finger flexion, thumb adduction, and thumb abduction. The aims of this evaluation system are to determine the relationships between early and late obstetric brachial plexus palsy, to predict the progressive changes that take place with aging, and to propose the possible operation procedures to reconstruct. However, this evaluation system may differ by time and may not be suitable for comparisons between pre- and postreconstruction.