Abstract—The Y chromosome of the spontaneously hypertensive rat (SHR) contains a genetic component that raises blood pressure compared with the Wistar-Kyoto (WKY) Y chromosome. This research tests the Sry gene complex as the hypertensive component of the SHR Y chromosome. The Sry loci were sequenced in 1 strain with a hypertensive Y chromosome (SHR/Akr) and 2 strains with a normotensive Y chromosome (SHR/Crl and WKY/Akr). Both SHR strains have 7 Sry loci, whereas the WKY strain has 6. The 6 loci in common between SHR and WKY strains were identical in the sequence compared (coding region, 392-bp 5' prime flanking, 1200-bp 3' flanking). Both SHR strains have a locus (Sry3) not found in WKY rats, but this locus is different between SHR/Akr and SHR/Crl rats. Six mutations have accumulated in Sry3 between the SHR strains, whereas the other 6 Sry loci are identical. This pattern of an SHR-specific locus and mutation in this locus in SHR/Crl coinciding with the loss of Y chromosome hypertension is an expected pattern if Sry3 is the Y chromosome–hypertensive component. The SHR/y strain showed a significant increase in total Sry expression in the kidney between 4 and 15 weeks of age. There are significant differences in Sry expression between adrenal glands and the kidney (15 to 30 times higher in kidneys) but no significant differences between strains. These results, along with previous studies demonstrating an interaction of Sry with the tyrosine hydroxylase promoter and increased blood pressure with exogenous Sry expression, suggest the Sry loci as the hypertensive component of the SHR Y chromosome.