The objective of the study was to evaluate the prevalence of medical contraindications in a large group of women seeking combined hormonal contraception (CHC).The Contraceptive CHOICE Project is a prospective cohort study designed to promote the use of long-acting reversible contraceptive methods to reduce unintended pregnancies in the St Louis region. During baseline enrollment, participants were asked about their desired methods of contraception and medical history. Potential medical contraindications were defined as self-reported history of hypertension, myocardial infarction, cerebral vascular accidents, migraines with aura, any migraine and age 35 years or older, smoking in women older than 35 years, venous thromboembolism, or liver disease. We reviewed all research charts of women with self-reported medical contraindications to verify all conditions. Binomial 95% confidence intervals (CIs) were calculated around percentages.Between August 2007 and December 2009, 5087 women who enrolled in the CHOICE Project provided information about their medical history and 1010 women (19.9%) desired CHC at baseline. Seventy women (6.93%; 95% CI, 5.44–8.68%) were defined as having a potential medical contraindication to CHC at baseline. After chart review, only 24 of 1010 participants desiring CHC (2.38%; 95% CI, 1.53–3.52%) were found to have true medical contraindications to CHC including 17 with hypertension, 2 with migraines with aura, 2 with a history of venous thromboembolism, and 3 smokers aged 35 years or older.The prevalence of medical contraindications to CHC was very low in this large sample of reproductive-aged women. This low prevalence supports provision of CHC without a prescription.