Over the past twenty-five years, several animal models of human essential hypertension have been produced through the development of inbred strains or lines of laboratory rats. The general availability of laboratory rats with genetically determined increases in arterial blood pressure has stimulated an impressive volume of research in the pathophysiology of experimental hypertension. In contrast, relatively little attention has been devoted to the study of behavioral correlates of experimental hypertension. In this review, I will evaluate the advantages and limitations of studying animal models of essential hypertension. Emphasis will then be placed on the relationship between stressful stimulation and behavioral and physiological responsiveness in two animal models of essential hypertension. Specifically, studies from my laboratory have examined sympathetic nervous system activity and behaviors of rats under basal conditions and following acute or chronic exposure to stressful stimulation. These findings indicate that the spontaneously hypertensive (SHR) strain is excessively responsive behaviorally and physiologically to a variety of stressful stimuli when compared to its Wistar-Kyoto (WKY) normotensive control strain. In contrast, the behavioral and physiological responses of New Zealand genetically hypertensive (GH) and normotensive (N) rats do not differ following acute exposure to stress. Thus, the hyperreactivity of SHR rats to stressful stimulation is not necessarily related to the development of hypertension but may be a valuable marker of the predisposition to develop high blood pressure in rats of the SHR strain. An experimental approach is outlined for examining the causal relationship between a genetically determined physiological or behavioral marker and the development of hypertension.