Heterotopic ossification is the most common extrinsic cause of elbow contracture and may lead to clinically important stiffness, and rarely, complete bony ankylosis. Surgery sometimes is performed to treat this problem, and published reports differ regarding the factors that are associated with success or failure after this operation and whether the procedure is effective for patients with elbow ankylosis. We wished (1) to identify potential patient characteristics and modifiable risk factors that are associated with improvements in ROM after surgery for heterotopic ossification of the elbow; (2) to compare ROM gains between patients with complete ankylosis and partially restricted ROM; and (3) to characterize the complications of elbows treated by surgical release and excision of heterotopic ossification followed by a standardized rehabilitation program. We reviewed the records of all patients treated operatively for heterotopic ossification of the elbow from September 1999 to February 2012 at one institution by one surgeon. General indications for the surgery were clinically symptomatic or debilitating heterotopic ossification of the elbow. Each patient received prophylaxis postoperatively consisting of indomethacin (or single-shot radiation for patients with sensitivity to antiinflammatory medications). All patients received a physical therapy regimen and used a continuous passive motion machine for 6 weeks. Patient demographics, mechanism of injury, time between injury and surgery, and medical history were reviewed for comparison. Followup was at a mean of 13 months (range, 3-106 months); no patients were lost to followup. Thirty-nine patients (46 elbows) with heterotopic ossification treated with excision were identified: 10 patients (16 elbows) had burns, 28 patients (29 elbows) had trauma, and one patient (one elbow) had a closed head injury. Eight of the 39 patients (12 of 46 elbows [26%]) had complete ankylosis at the time of surgery. Hypertension, obesity, and absence of intraoperative anterior ulnar nerve transposition were associated with an adverse effect on change from preoperative to final arc of motion. The group with ankylosis had greater preoperative to postoperative gain in arc compared with the group with partial restriction (96°, 95% CI, 84°-107° and 59°, 95% CI, 46°-72°, respectively). For the entire cohort there was an overall improvement in mean flexion-extension arc of motion from 35° to 103° at final followup (p < 0.001; 95% CI, 57°-80°), with a 17% rate of complications (three patients [three elbows] with heterotopic ossification, three patients [three elbows] with nerve palsies, one patient [one elbow] with deep wound infection, and one patient [one elbow] with an unstable elbow). Patients with partially and completely restricted ROM showed substantial improvement in postoperative ROM. Hypertension, obesity, and absence of intraoperative anterior ulnar nerve transposition were negative predictors of outcome in our series. Surgery combined with postoperative prophylaxis and a regimented rehabilitation program are feasible modalities to treat patients with heterotopic ossification of the elbow. Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.