Heterotopic ossification (HO) after femoral intramedullary rodding is a significant complication of the procedure. One hundred eighteen cases of femoral roddings performed on 113 patients were available for review. The data were computerized and evaluated using univariate analysis and multivariate regression analysis. A statistically significant increase of HO was found with male gender, increased delay to surgery, and in patients requiring prolonged intubation because of their multiple injuries. HO was classified using a modified version of the method of Brumback et al. (grades 0-IV). A strong correlation of HO with brain injury documented by computed tomography scan was also found to be statistically significant for the more severe grades of HO. This group of patients had not previously been identified as being at high risk for HO.