Several antihypertensive drugs have an adverse effect on glucose tolerance that may partially or completely negate the beneficial effects of reducing blood pressure as it relates to the incidence of coronary heart disease and its complications. Diuretics (particularly high doses) and beta-blockers without intrinsic sympathomimetic activity have the greatest adverse effect on glucose intolerance. Central alpha-agonists, angiotensin-converting enzyme inhibitors, calcium channel blockers, and alpha-blockers do not adversely affect glucose and are preferred in diabetic hypertensive patients, selected hypertensive patients at risk for developing glucose intolerance, and probably most other patients with mild essential hypertension as initial and/or monotherapy compared with diuretics and beta-blockers.