The influence of maternal environment on the development of high blood pressure in spontaneously hypertensive (SHR) and Dahl salt-sensitive (SS/Jr) rats was examined using the technique of reciprocal cross-fostering. Previous experiments from this laboratory demonstrated that adult blood pressures of the SHR and SS/Jr strains were significantly attenuated when hypertensive-strain pups were fostered to a dam of the respective normotensive control strain during the preweaning period. In this study, SHR and SS/Jr pups were assigned to either a cross-fostered (fostered to a dam of the opposite hypertensive strain) or control-reared condition within 24 h of birth. Adult resting blood pressures were similar in control and cross-fostered SHR rats and in control and cross-fostered SS/Jr rats. Heart rates and heart, adrenal, and kidney weights were also similar in control and cross-fostered rats of each strain. However, body weights of SHR rats reared by an SS/Jr dam were somewhat lower compared to control-reared SHR rats. These data indicate that the maternal environments provided by SHR and SS/Jr mothers are similar in some way such that they permit the development and full expression of the hypertensive phenotype in both same-strain and opposite-strain pups.