Primary or 'essential' hypertension is generally perceived to be a mul
tifactorial or complex genetic trait. An individual's susceptibility t
o high blood pressure (BP) is influenced not only by the many genetic
factors, which effect control through biochemical and physiological me
chanisms, but also by environmental determinants. In a small proportio
n of human hypertensives the cause is a single genetic defect, exhibit
ing Mendelian characteristics. The vast heterogeneous majority, howeve
r, result from a multitude of contributing factors, making identificat
ion of the underlying etiology very difficult. We will briefly review
a number of strategies which have helped to identify genetic factors i
nvolved in hypertension. These include the search for genetic defects
in Mendelian forms of hypertension, intensive study of classical anima
l models such as the spontaneously hypertensive rat, and linkage analy
ses in animal models and hypertensive patients. We will then discuss t
he role which transgenesis can play in complementing and extending suc
h analyses.