Treatment with angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) during pregnancy can cause severe foetal abnormalities. This study aimed to identify the proportion of women of childbearing age taking ACE inhibitors or ARBs on referral to a tertiary Hypertension Clinic. Retrospective cohort study. A cohort of female patients aged 16-45 years was identified from approximately 1500 new referrals from January 2004 to October 2006, excluding those not taking antihypertensive medication. ACE inhibitors and ARBs were grouped together for the purposes of the study. Contraceptive status was established where possible. Forty seven of 101 (47%) women aged 16-45 years were taking an ACE inhibitor (35) an ARB (11) or both (1) of whom 26 (55%) were aged 16-40 years. In this younger group, eight were using no contraception and three were using barrier methods only. Many GPs continue to prescribe ACE inhibitors and ARBs to women of childbearing age. A quarter of women in the study were taking these agents and were 40 years or less; of these many were not using reliable contraception. These women are at risk of foetal malformation and poor perinatal outcomes if they become pregnant. The British Hypertension Guidelines may put younger women at risk if general practitioners are unaware of potential foetotoxic and teratogenic consequences of prescribing ACE inhibitors and ARBs to women of child bearing age.