OBJECTIVE The purpose of this study was to classify Galeazzi type injuries and determine the association of residual instability after rigid fixation with the fracture pattern of the shaft of the radius, using a system that is based on anatomic landmarks of the radial shaft. METHODS The clinical records of 95 patients (72 men and 23 women) with Galeazzi type injuries requiring open reduction and internal fixation of the fractures were retrospectively reviewed. The mean follow-up was 6.8 years (range, 18 mo to 11 y) after injury. Sixty-nine fractures occurred in the distal third of the radial shaft (type I), 17 fractures were in the middle third (type II), and 9 fractures were in the proximal third of the shaft of the radius (type III). Gross instability of the distal radioulnar joint (DRUJ) was determined intraoperatively by manipulation after radial fixation as compared to the uninjured side. RESULTS Forty patients had DRUJ instability after internal fixation and were treated with temporary pinning with a K-wire placed transversely proximal to the sigmoid notch. Distal radioulnar joint instability after internal fixation was recorded in 37 type I fractures, 2 type II fractures, and 1 type III fracture. CONCLUSIONS Distal radioulnar joint instability following radial shaft fracture fixation is significantly higher in patients with type I fractures than in patients with type II or type III fractures. The location of the radius fracture can be sufficiently used for preoperative estimation of percentage chance of potential DRUJ instability after fracture fixation.