Injury to the peroneal tendons is one of the major long-term complications of intraarticular calcaneal fractures and heretofore has been difficult to diagnose by noninvasive radiography. Retrospective review of CT scans of 24 intraarticular calcaneal fractures, obtained shortly after injury, identified 22 cases (92%) of acute peroneal tendon abnormalities. In most of these cases, multiple findings were present. These included lateral displacement in 14 (58%) of 24, impingement by bony fragments in eight (33%), subluxation or dislocation in six (25%), soft-tissue masses around the tendons representing hematomas or early scar tissue in five (21%), and entrapment of the tendons in three (13%). In 10 cases with long-term follow-up, impingement on the tendons by bony fragments correlated well with the subsequent development of peroneal tenosynovitis, while hematoma around the tendons or lateral displacement of the tendons was clinically insignificant. Thus, CT in the immediate postfracture period, can be used to detect and categorize acute peroneal tendon injuries as well as possibly to predict the likelihood and nature of subsequent development of peroneal tenosynovitis.