OBJECTIVE: To compare the estimated proportion of contraindications to combined oral contraceptives between women who obtained combined oral contraceptives in U.S. public clinics compared with women who obtained combined oral contraceptives over the counter (OTC) in Mexican pharmacies. METHODS: We recruited a cohort of 501 women who were residents of El Paso, Texas, who obtained OTC combined oral contraceptives in Mexico and 514 women who obtained combined oral contraceptives from family planning clinics in El Paso. Based on self-report of World Health Organization category 3 and 4 contraindications and interviewer-measured blood pressure, we estimated the proportion of contraindications and, using multivariable-adjusted logistic regression, identified possible predictors of contraindications. RESULTS: The estimated proportion of any category 3 or 4 contraindication was 18%. Relative contraindications (category 3) were more common among OTC users (13% compared with 9% among clinic users, P=.006). Absolute contraindications (category 4) were not different between the groups (5% for clinic users compared with 7% for OTC users, P=.162). Hypertension was the most prevalent contraindication (5.6% of clinic users and 9.8% of OTC users). After multivariable adjustment, OTC users had higher odds of having contraindications compared with clinic users (odds ratio [OR] 1.59, 95% confidence interval [CI] 1.11-2.29). Women aged 35 years or older (OR 5.30, 95% CI 3.59-7.81) and those with body mass index 30.0 or more (OR 2.24, 95% CI 1.40-3.56) also had higher odds of having contraindications. CONCLUSION: Relative combined oral contraceptive contraindications are more common among OTC users in this setting. Progestin-only pills might be a better candidate for the first OTC product given their fewer contraindications.