Clinical and roentgenographic observations on a postoperative low-dose radiation of 1000 cGy for prevention of heterotopic ossification in high-risk patients after 48 noncemented total hip arthroplasties demonstrated no overall statistical difference in the Harris hip scores between the treated group (92.2) and the control group (91.0). There was no difference in the incidence of radiolucent lines about the components, and there were no revisions for aseptic loosening in the treated group. The incidence of clinically significant (Brooker Grades III and IV) heterotopic bone formation was lower in the treated group (7%) than in the control group (32%). This difference in the incidence of heterotopic bone formation was statistically significant. Radiation therapy was effective in preventing postoperative heterotopic bone formation in biologically fixed total hip implants.