Hello Laura Caston,   Both medications can help you lower you blood pressure.    Dyazide is a combination of triamterene and hydrochlorothiazide, both of which are diuretics; these drugs lower your blood pressure by decreasing the amount of water in your blood vessels.    Benicar works in a completely different way.  Benicar, of the ARB (aka angiotensen receptor blocker class), works by blocking the action of a hormone in the body that both dilates the blood vessels and increases the amount of water in the blood.   Both drugs are safe, well-tolerated, and effective in reducing pressure; depending on your health insurance, cost may end up being the most important factor in deciding which medication you take.    To your health, Neil MD