BACKGROUND The purpose of this retrospective study was to analyze the functional results following open reduction and internal fixation of fractures of the radial head and to determine which fracture patterns are most amenable to this treatment. METHODS Fifty-six patients in whom an intra-articular fracture of the radial head had been treated with open reduction and internal fixation were evaluated at an average of forty-eight months after injury. Thirty patients had a Mason Type-2 (partial articular) fracture, and twenty-six had a Mason Type-3 (complete articular) fracture. Twenty-seven of the fifty-six fractures were associated with a fracture-dislocation of the forearm or elbow or an injury of the medial collateral ligament. Fifteen of the thirty Type-2 fractures were comminuted. Fourteen of the twenty-six Type-3 fractures consisted of more than three fragments, and twelve consisted of two or three fragments. The result at the final evaluation was judged to be unsatisfactory when there was early failure of fixation or nonunion requiring a second operation to excise the radial head, <100 degrees of forearm rotation, or a fair or poor rating according to the system of Broberg and Morrey. RESULTS The result was unsatisfactory for four of the fifteen patients with a comminuted Mason Type-2 fracture of the radial head; all four fractures had been associated with a fracture-dislocation of the forearm or elbow, and all four patients recovered <100 degrees of forearm rotation. Thirteen of the fourteen patients with a Mason Type-3 comminuted fracture with more than three articular fragments had an unsatisfactory result. In contrast, all fifteen patients with an isolated, noncomminuted Type-2 fracture had a satisfactory result. Of the twelve patients with a Type-3 fracture that split the radial head into two or three simple fragments, none had early failure, one had nonunion, and all had an arc of forearm rotation of > or =100 degrees. CONCLUSIONS Although current implants and techniques for internal fixation of small articular fractures have made it possible to repair most fractures of the radial head, our data suggest that open reduction and internal fixation is best reserved for minimally comminuted fractures with three or fewer articular fragments. Associated fracture-dislocation of the elbow or forearm may also compromise the long-term result of radial head repair, especially with regard to restoration of forearm rotation.