Introduction: It is assumed that sexual assault cases presenting at Emergency Departments (ED) are frequently lost to follow-up and should be considered an eligible population for presumptive antimicrobial treatment of sexual transmitted infections (STIs) at initial assessment without lab confirmation. With the growing burden of antibiotic resistance, antimicrobial stewardship guidelines caution against this practice. Among sexual assault cases, our study evaluated STI prevalence, follow-up and retention patterns, and described the prevalence of STI presumptive treatment. Methods: The Sexual Assault and Partner Abuse Care Program (SAPACP) at The Ottawa Hospital is the only program in Ottawa offering emergency and forensic care for survivors of sexual assault and domestic violence. Descriptive statistics were used to summarize information on demographics, clinical presentation, STI testing and results using data from the SAPACP case registry (January 1 - December 31, 2015). Results: Among the 406 patients seen by the SAPACP, there were 262 (64.5%) sexual assault cases that were included in this analysis. STI testing was completed for 209 (79.8%) patients at the initial visit, 90 (43.1%) completed via urine nucleic acid testing (NAAT), 140 (67.0%) via culture swab and 20 (9.6%) via both. Laboratory results detected no cases of gonorrhea, 8 (3.8%) cases of chlamydia, 33(15.8%) cases of bacterial vaginosis (BV), 17 (8.1%) cases of yeast vaginitis and 16 (7.7%) indeterminate testing results. Antimicrobial STI presumptive treatment was given to 12 (5.7%) patients at the time of their initial visit prior to lab confirmation. Patient follow-up occurred in 172 (82.3%) patients, with all chlamydia cases treated. Of the 37 (17.7%) patients lost to follow up, 9 were positive for BV, 1 was positive for yeast and 10 were indeterminate, all of which may be underlying vaginal flora. Follow up testing/test of cure was completed in 91 (52.9%) of patients, with 4 (2.3%) positive results, all of which were BV. Conclusion: In our ED, up to 15.8% of sexual assault patients had at least one laboratory confirmed STI and over 80% of all patients returned for follow-up. Our results show that it is safe and effective to only treat STI screen positive cases at follow-up, reducing the frequency of presumptive antimicrobial STI treatment. Benefits of this strategy include decreased patient side effects, cost savings and better antimicrobial stewardship.