Anatomic dissections have suggested that mobilization of the supraspinatus and infraspinatus tendons greater than 1 cm may cause suprascapular nerve injury. This study evaluated rotator cuff function by use of electromyographic (EMG) analysis after primary repair of massive tears in 9 patients. All subjects had massive rotator cuff tears involving at least the entire supraspinatus and entire infraspinatus tendons. Rotator cuff advancement averaged 2.5 cm (range, 2.0-3.5 cm). No EMG evidence of suprascapular nerve injury was found postoperatively. The UCLA shoulder score improved from a preoperative mean of 11 to a postoperative mean of 28. There was 1 excellent, 6 good, 1 fair, and 1 poor result. The poor result was due to a documented failed repair. The EMG results suggest that mobilization and advancement of the rotator cuff up to 3.5 cm during primary repair may be performed safely without as much risk to the suprascapular nerve as anatomic studies would suggest.