British researchers studied a huge cohort of 992 061 patients newly treated with antihypertensive drugs using Cox proportional hazards models were to estimate adjusted hazard ratios with 95% confidence intervals of incident lung cancer that were associated with use of ACE Inhibitors, and comparing these to those associated with treatment to Angiotensin Receptor Blockers ARBs) The cohort was followed for a mean of 6.4 years, and 7952 incident lung cancer events were observed (crude incidence 1.3 (95% confidence interval 1.2 to 1.3) per 1000 person years). Use of ACE Inhibitors was associated with an increased risk of lung cancer (incidence rate 1.6 v 1.2 per 1000 person years; hazard ratio 1.14, 95% confidence interval 1.01 to 1.29), compared with use of ARBs. Hazard ratios gradually increased with longer durations of use, with an association evident after five years of use (hazard ratio 1.22, 1.06 to 1.40) and peaking after more than 10 years of use (1.31, 1.08 to 1.59). The authors in this study, published in the British Medical Journal this week, invoke several mechanisms for biological plausibility.