The accuracy of high-resolution real-time ultrasonic examination of the flexor tendons of the fingers was tested in a retrospective study of 27 patients treated surgically. In ruptured tendons (8 cases) the method proved sensitive and specific, except in cases of partial rupture. Ultrasound made it possible to distinguish between extrinsically developed palmar masses (8 cases) and masses involving the tendons (4 cases). A fluid collection inside the tendon sheath was detected in 5 cases of tenosynovitis, without false-positive results. The post-operative follow-up of surgically treated tendons (2 cases) was easier with ultrasound.