Ultrasound (US) has recently become a favorable diagnostic technique in orthopedics and traumatology, as well as in other medical sciences. We aimed to determine effectiveness of US in diagnosis of soft tissue interposition that impedes or delays the union of fracture. The present study included 55 acute fractures in 39 patients, in whom operation (open reduction and internal fixation) was scheduled because no closed reduction was achieved, in our department between January 1999 and December 2003. Before the operation, the fracture line in all patients was scanned by a 5- to 7-MHz linear probe of the US device. The data obtained by US examination were compared to findings obtained by surgical intervention with the McNemar test. These were calculated as positive predictive value and negative predictive value, with specificity and sensitivity. The difference between the study and control groups was not statistically significant (p = 0.625). These findings demonstrated that sensitivity value, specificity value, positive and negative predictive values were 96.9%, 86.3%, 91.4% and 95%, respectively. US is an efficient, safe and reliable diagnostic technique for detection of interposition of soft tissue in bone fracture line. (E-mail: email@example.com) (C) 2006 World Federation for Ultrasound in Medicine & Biology.