Fifty-seven patients had secondary treatment for laceration of the flexor pollicis longus tendon: by direct repair in nine patients, tendon advancement with or without lengthening at the wrist in twenty-three, free tendon-grafting in eighteen, and tendon transfer in four, the method of treatment depending on the location of the laceration. Based on the results in these patients, it was concluded that for lacerations distal to the metacarpophalangeal joint, advancement of the proximal tendon segment combined with lengthening at the wrist, as needed, is the preferred treatment. Preliminary experiments in chickens designed to compare vascularization after different methods of tendon repair showed no differences in this respect, but there were fewer peritendinous adhesions and the histological appearance of the tendon was more normal in the initial phases of healing after advancement than after grafting.