Thirteen injured digits in 10 patients (10 hands) with 20 potentially injured flexor tendons were preoperatively evaluated using real-time ultrasonography. The time interval between injury and ultrasonographic evaluation averaged 22 days. If a complete tendon laceration was found, the location of the proximal tendon stump was determined. Surgery was performed an average of 4 days after the ultrasonographic evaluation to determine the accuracy of the ultrasound study. Ultrasonography accurately identified the status of the flexor tendon in 11 of 13 digits and in 18 of 20 flexor tendons (12 intact, 2 partial lacerations, and 6 complete tendon lacerations). With complete tendon lacerations the location of the proximal tendon stump was accurately identified in 5 of 6 digits. There were 2 false ultrasound findings, including incorrectly identifying a 75% laceration in an intact index flexor and a complete tendon laceration in a 75% lacerated index finger flexor. Ultrasonography can help to evaluate the preoperative status of injured flexor tendons and, in cases of completely lacerated tendons, can help identify the location of the proximal tendon stump. (C) 2000 by the American Society for Surgery of the Hand.