Our own research has focused on the stroke-prone spontaneously hypertensive rat (SHRSP), where the genetic determination of hypertension is due to multiple gene–gene and gene–environment interactions. Although exceptionally high blood pressure is clearly a factor for end-organ damage in the SHRSP, genetic factors are also likely to contribute. In particular, two blood pressure QTLs have been mapped to rat chromosome 2 [37]. This region of chromosome 2 is a classic example of a common or overlapping QTL because it has been implicated in several rat crosses. These two QTLs, therefore, have become a focus for further congenic strategies in our laboratory [38] and other laboratories [39]. In combination with congenic strain construction in the SP.WKYGla2a and SP.WKYGla2c* strains, genome-wide microarray expression profiling identified glutathione S-transferase mu type 1 (Gstm1) as a positional candidate gene for spontaneous hypertension [40], [41] and [42], and endothelial differentiation gene 1 (Edg1) and vascular cell adhesion molecule 1 (Vcam1) for salt sensitivity [43].