This study tests the hypothesis that dietary NaCl loading increases cerebrospinal fluid (CSF) Na+ concentration in NaCl-sensitive spontaneously hypertensive rats (SHR-S), resulting in an increase in arterial pressure. The high NaCl diet caused a significant rise in systolic arterial pressure in SHR-S but not in normotensive Wistar Kyoto (WKY) rats. In contrast, the high NaCl diet caused a transient rise in CSF Na+ that was similar in amplitude in SHR-S and WKY. A second experiment demonstrated that in SHR-S, concomitant dietary Ca2+ supplementation attenuated the dietary NaCl-induced exacerbation of hypertension, but did not alter the transient increase in CSF Na+ concentration. Together, these results indicate that alterations in CSF Na+ concentration do not contribute to the increase in arterial pressure induced by a high NaCl diet in SHR-S. © 1990.