Hypertension and proteinuria in pregnancy may be the result of a number of different disorders with different etiologies and pathologic characteristics. As the causes of hypertension and proteinuria in pregnancy are largely unknown, a new clinical classification of the hypertensive disorders is proposed and is based solely on the physical signs of hypertension and proteinuria. The classification is intended to define meaningful clinical categories by which all cases of hypertension and proteinuria occurring in pregnancy, labor, or the puerperium may be classified. New definitions of hypertension and proteinuria are also proposed; they are based on standardized methods of measurement and simple criteria of abnormality. It is hoped that this clinical classification and associated definitions will find general acceptance so that the incidence and outcome of the hypertensive disorders of pregnancy and the results of research in different centers may be compared and mutual understanding achieved.