There are conflicting reports on cancer risk associated with angiotensin-converting enzyme (ACE) inhibitors/angiotensin receptor blockers (ARBs). This retrospective cohort study was conducted to analyze the risk of cancer development in patients who received ACE inhibitors/ARBs as treatment for essential hypertension. Using the Taiwan National Health Insurance Research Database, 297,688 eligible study patients with essential hypertension were identified. According to their antihypertensive prescriptions, the study patients were stratified into an ACE inhibitor group, an ARB group, or a control group. After matching, participants were observed for the occurrence of cancer. In the ACE inhibitor group compared with the control group, the hazard ratio was 0.51 (95% confidence interval, 0.39-0.68). In the ARB group compared with the control group, the hazard ratio was 0.8 (95% confidence interval, 0.65-0.97). Regular use of ACE inhibitors/ARBs was not associated with an increased risk of cancer development and was actually found to decrease overall cancer risk in this study.