The relationship between the use of anti-hypertensive drugs and cancer risk remains controversial.The main objective of this study was to assess the effects of beta-blocker use on cancer risk. Methods:In a cohort of 839 patients with cardiovascular disease, followed up prospectively for a mean of 10years, we compared the risk of cancer in subjects who had and had not received beta-blockers. We estimated therelative risk of cancer associated with beta-blocker use with a Cox model adjusted for sex and age. The use ofbeta-blockers and the duration of exposure to the drug were analyzed as time-dependent variables. We alsocalculated standardized incidence ratios (SIR) from the corresponding age- and sex-adjusted cancer incidencesin the French general population. Results: A total of 326 beta-blocker users and 513 subjects on other treatments were included in the cohort.During the follow-up period, corresponding to 8,466 person-years, 15 incident cancer cases occurred in beta-blocker users and 59 occurred in patients who had never used beta-blockers. The Cox model estimated theoverall relative risk of cancer at 0.51 (95% confidence interval [CI]: 0.29-0.90) in the beta-blocker users,compared with those who had never used beta-blockers (p= 0.02), with a 6% decrease per year of use (95% CI:1%-12%p= 0.03). The corresponding SIR ratio between these two groups was 0.44 (CI: 0.24-0.76) Conclusion: In this cohort, beta-blocker treatments appeared to decrease the risk of cancer significantly.However, this result should be interpreted with caution, as biases inherent in this type of epidemiologicalstudy cannot be totally excluded.