Several studies have suggested that antihypertensive treatment may promote cancer through unknown mechanisms. Early retrospective studies implicated reserpine in breast cancer, but data from prospective studies and meta-analysis of several case-controlled studies showed only a weak association between reserpine and breast cancer which, although statistically significant, is of little clinical concern. Data from case-controlled studies and several cohort studies suggested an association between the use of a diuretic and the occurrence of renal cell cancer, particularly in women. A recent study showed an association between the use of a diuretic and the occurrence of colon cancer. Several prospective studies showed that treatment with atenolol may increase mortality from malignancy. However, other studies that analyzed data from several thousand patients could not confirm this association. In three prospective and a few case-controlled studies, angiotensin converting enzyme inhibitors were not associated with increased mortality from malignancy. In addition, a recent retrospective study showed that long-term use of angiotensin converting enzyme inhibitors had a protective effect against malignancy. Data from three large case-controlled studies and the combined data from eight randomized controlled studies and seven longitudinal studies showed a similar risk for malignancy among users and nonusers of calcium antagonists. Until further data from prospective clinical trials are available, we advise caution about long-term diuretic therapy in women. With regard to other antihypertensive drug classes, we suggest continuing the management of hypertension according to current treatment guidelines with little fear of any substantial cancer risk.