Background: NRG-RTOG 1203 reported that intensity-modulated radiation therapy (IMRT) reduced patient-reported GI and GU toxicities in cervical/endometrial cancer patients receiving adjuvant RT, as compared to standard whole field pelvic RT (WPRT). We conducted a secondary analysis of patient-reported sexual function (PR-SF) to compare this endpoint among treatment groups and identify factors associated with sexual dysfunction. Methods: Patients on NRG-RTOG 1203 were randomly assigned to WPRT vs. IMRT and completed the PRO-CTCAE for GI toxicity and the cervical cancer FACT-Cx at baseline, week 5 of RT, and at 4-6 weeks, 1-year, and 3-years post-RT. Patient responses to FACT-Cx sexual function questions were analyzed. The between arm frequency and severity of responses were tested using chi-square. PR-SF was compared with PRO-CTCAE GI toxicity using chi-square. A repeated measures logistic regression model was used to determine the impact of clinical/treatment factors on sexual function by dichotomizing the responses. Results: Of the 279 patients included for primary analysis, 236 (85%) completed PR-SF questions; 125 (53%) in the WPRT arm and 111 (47%) IMRT. There were no significant differences in PR-SF between treatment groups (p>0.05). PR-SF improved for both groups post-RT, except responses to “my vagina feels too narrow or short” worsened (Table). Women without abdominal pain interference at 4-6 weeks post-RT were less likely to fear sex (74.2% vs. 25.8%, P=0.03) and more likely to like their body appearance at 1 year (95.7% vs. 4.3%, P<0.01) compared to women with interference. Women liked the appearance of their body less during RT vs. at baseline (OR 1.95, 95% CI 1.04-3.64, P=0.04). Women were less interested in sex during RT in both arms (WPRT: OR 3.61, 95% CI 1.40-9.34; IMRT: OR 3.96, 95% CI 1.02-15.34) and at 4-6 weeks post-RT for IMRT (OR 3.16, 95% CI 1.14-8.72) vs. at baseline. Conclusions: PR-SF was similar between treatment groups. PR-SF during and post-RT was not significantly reduced compared to baseline with the exception of patients with abdominal pain interference, who had significantly worse PR-SF at 4-6 weeks and 1-year post-RT. Clinical trial information: NCT01672892.