The J-curve in hypertension treatment refers to the relationship between achieved diastolic blood pressure (BP) and cardiovascular morbidity and mortality, specifically related to coronary heart disease (CHD). As diastolic BP decreases below a certain threshold or nadir, the risk of cardiovascular events increases. This phenomenon was first described over 30 years ago and its significance has been debated ever since. We review in detail the literature for and against the existence of this J-curve and discuss its purported pathophysiology. Most notably, recent post hoc analyses of large contemporary randomized trials in patients with documented CHD strongly support its existence. Given the current emphasis on strict BP control, especially in high-risk patients like those with CHD, diabetes, and chronic kidney disease, we discuss the implications this J-curve may have for treating hypertension in the individual patient.