Commentary on epidemiological studies and intervention trials.

Epidemiological studies have proved invaluable for identifying environmental risk factors and gene-environment interactions in the development of hypertension and other chronic diseases. Now, after several decades, the solid contributions of longitudinal and cross-national studies of random population samples are well established. The art and science of clinical trials have achieved a high level of sophistication and have given clear answers to questions of great importance to public health. No other form of experimentation could have provided this kind of data. It has had an incalculable influence on clinical practices and on nonpharmacological approaches to the prevention of disease throughout the world.