This study examines the effects of a 6-week exposure to 1% NaCl in tap water with and without desoxycorticosterone acetate (DOCA) on renal alpha adrenoceptors and systolic blood pressure (SBP) in spontaneously hypertensive adult rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. On normal sodium intake, SHR had higher renal alpha 1- (p less than 0.05) and alpha 2-adrenoceptor densities (p less than 0.001) and SBP (p less than 0.001) than WKY rats. Although WKY rats given either 1% NaCl, DOCA, or DOCA plus 1% NaCl developed hypertension after 6 weeks of treatment, only 1% NaCl administration for the same period produced an increase in the alpha 1-adrenoceptor density when compared to the control (p less than 0.001). In SHR, ingestion of 1% NaCl or DOCA plus 1% NaCl increased the already elevated alpha 2-adrenoceptor density (p less than 0.001) and SBP even more in this strain after 6 weeks of treatment. Equilibrium dissociation constants (Kd), however, were similar for both classes of receptors in experimental and control rats. The results of this study indicate that only the combination of 1% NaCl in tap water and DOCA administration is effective in accelerating hypertension in adult SHR. On the other hand, in this form of genetic rat hypertension, exaggerated sodium intake with or without DOCA administration could presumably be correlated with the increased renal alpha 2 adrenoceptors observed in these animals.