The objective of this study was to examine the response of tissue steroid sulfatase (STS) levels in hypertensive rat strains, when blood pressure (BP) was lowered by different techniques at an early age. A 4x3 factoral design was used, in which males (n=6-8) from four rat strains (WKY, SHR, SHR/a, SHR/y) at 4 weeks of age, were randomly assigned to one of three treatment groups: a hydralazine group, a castration group and a control group. BP was measured by the tail cuff technique and verified by tail catheter at the end of the experiment. BP was significantly reduced by both treatments in the hypertensive strains (SHR, SHR/a, SHR/y) compared to respective control groups. At 15-17 weeks of age, animals were euthanized and heart, kidney, adrenal glands and liver were assayed for STS levels. The major trend in tissue STS was that castration significantly lowered: adrenal, heart and liver STS in specific strains. In conclusion, castration and hydralazine significantly lowered the BP in the hypertensive rat strains, but only castration consistently lowered STS levels across strains implicating testosterone as a regulator of tissue STS.