In the spontaneously hypertensive rat (SHR) increased carbohydrate intake without alteration in sodium intake is associated with elevated blood pressure. One week of feeding sucrose-supplemented chow increased blood pressure an average of 14mm Hg (9%) in three separate groups of SHR, but did not affect blood pressure in normotensive rats of the same strain (Wistar-Kyoto-WKY). Fat supplementation (isocaloric to sucrose) was without effect on blood pressure in SHR. These data are consistent with the hypothesis that diet-induced increases in sympathetic activity may elevate blood pressure in susceptible animals.