Objective: To evaluate if the combination of both prone position on a belly board and intensity-modulated radiotherapy (IMRT) further reduces the radiation dose to small bowel in pelvic RT for gynecologic malignancies. Methods: Conformal pelvic RT plans were computed in 13 patients with gynecologic malignancies who had pre-existing planning computed tomography (CT) scans in both the supine position and prone position on a belly board. There were 10 cervical cancer and 3 endometrial cancer patients. A limited arc technique (180° arc length) and an extended arc technique (340° arc length) were used in IMRT plans. Normal tissue regions of interest (ROI) included small bowel, large bowel and bladder. Dose and volume for normal tissue structures were traced and compared between supine and prone plans using the paired t-test. Results: For the limited arc technique, prone position using a belly board device improved small bowel sparing. Analysis of the results showed a 12(26 Gy reduction of volume of small bowel irradiation compared to the supine position. With the extended arc technique, there was no obvious radiation reduction in the prone position. Large bowel and bladder dose showed no significant differences between prone and supine position with either technique. Conclusion: Prone positioning on a belly board decreases the small bowel dose in gynecologic pelvic IMRT, and the magnitude of improvement depended on the limited arc IMRT technique used.