To describe intravaginal practices (IVPs) among female sex workers (FSWs) who inject drugs in two cities-Tijuana and Ciudad Juarez-on the border between the USA and Mexico.Data for a secondary analysis were obtained from interviews conducted as part of a randomized controlled trial in FSWs who injected drugs between October 28, 2008, and May 31, 2010. Eligible individuals were aged at least 18years and reported sharing injection equipment and having unprotected sex with clients in the previous month. Descriptive statistics were used to assess frequency and type of IVPs. Logistic regression was used to assess correlates of IVPs.Among 529 FSWs who completed both surveys, 229 (43.3%) had performed IVPs in the previous 6months. Factors independently associated with IVPs were reporting any sexually transmitted infection in the previous 6months (adjusted odds ratio [aOR] 1.8, 95% confidence interval [CI] 1.1-3.1; P=0.03), three or more pregnancies (aOR 1.9, 95% CI 1.1-3.2; P=0.02), and having clients who became violent when proposing condom use (aOR 5.8, 95% CI 1.0-34.3; P=0.05), which are all factors related to inconsistent condom use.Screening for IVPs could help to identify FSW at increased risk of HIV, and facilitate conversations about specific risk-reduction methods.