Results of the treatment of non-union of fractures of long bones by internal fixation are reported. Two standard stainless-steel bone plates, applied at an angle of 90 degrees to each other, were utilized in the treatment of fifty-nine fractures with non-union in fifty patients. Fifty-one fractures were followed long enough to permit analysis of the results. Successful union occurred in forty-eight, an incidence of 94.1 per cent. Of the fractures in which this treatment resulted in failure, one united after plate removal, control of infection, and immobilization in a plaster cast; another was replated with resultant union; and the third remained a failure because of infection. The two-plate rigid fixation makes unnecessary, in most cases, the use of external immobilization and affords immediate rehabilitation of adjacent joints. A bone graft, other than that obtained locally, is usually unnecessary and was utilized in only one case in this series. The two-plate method has proved to be clinically successful and mechanically sound. Although it requires considerable mechanical skill and attention to detail, it has become the authors' preferential technique in the treatment of non-union of fractures of long bones.