Massive and irreparable rotator cuff tears are a challenge for the orthopaedic surgeon. The purpose of this study was to report our experience with the treatment of massive and irreparable defects of the rotator cuff with a modified deltoid split transfer. Between 1996 and 2004, for all patients suffering from full-thickness tears of the rotator cuff (> 5 cm tears in diameter, involving two or more tendons) were operated with a modified deltoid split transfer. A total of 61 patients (39 females and 22 males; age 61.9: range 49-75 years) were operated. Duration of symptoms before surgery averaged 9.6 months (range 3.5-14 months). The patients were followed for an average of 46 months (range 24-64 months). The operation included an arthroscopic evaluation, acromioplasty with resection of the lateral clavicular end, resection of the acromioclavicular joint and where necessary biceps tenodesis. The cuff defect was repaired by transfer of half thickness anterior deltoid-flap (3 cm x 5 cm) into the defect. All patients were evaluated both preoperatively and postoperatively with regard to pain, ability to perform activities of daily life, range of motion, strength and satisfaction. The patients subjectively rated their results--49 (80%) excellent or good outcome, seven moderate and five poor. Preoperatively, the Constant amounted 33.5 +/- 7.74 points. At follow-up, the score significantly increased to 77.57 +/- 19.74 points. The acromiohumeral distance increased from 5.1 +/- 1.4 mm to 9.1 +/- 1.5 mm. Pain free flexion improved from an average 90 degrees to an average 165 degrees (P < 0.01), and abduction improved from an average 110 degrees to an average 160 degrees (P < 0.01). The mean external rotation increased from 40 degrees to 65 degrees (P < 0.01), and internal rotation increased from 50 degrees to 70 degrees (P = 0.06). In the MRI and ultrasound examination, all patients had intact flap, except the three patients with flap necrosis. There were eight complications--three haematomas, two superficial wound infections which did not influence the outcome, and three fibrotic transformation after an early aseptic necrosis of the deltoid flap, which were re-operated. This technique is easy to perform, and it is possible to obtain a satisfactory outcome after repair of massive tears of the rotator cuff. A substantial decrease of pain, increased stability, an increase range of motion and strength can be achieved, with proper rehabilitation.