Transfer of a flexor digitorum superficialis tendon is an effective procedure in restoring active flexion of the thumb following old lacerations or ruptures of the flexor pollicis longus tendon within the digital sheath when tendon repair or advancement is not possible. The ample length of the transferred tendon and, more importantly, its normal excursion make it the preferred procedure to the alternative tendon graft. The operation is usually carried out as a one-stage procedure, but, if there is severe scarring, it can follow the preliminary insertion of a silicone rod. For 23 patients, the operation was performed in a single stage in 18 and in 5 after insertion of a silicone rod. Postoperative mobility of the interphalangeal joint averaged 53.5 degrees. Mobility of the donor ring finger was complete in all patients.