We have recently reported that the allele of the SA gene of the Spontaneously hypertensive rat (SHR) has a capacity to influence blood pressure in a F2 rat population prepared from SHR and Wistar-Kyoto rat. In the present study, we have undertaken a similar genetic co-segregation analysis of the F2 rat population prepared from SHR and Lewis rat. The result indicated that, although overall effects of the SA gene genotypes on blood pressure were not significant, a correlation of the genotypes of the SA gene with blood pressure was significantly observed in the female rats of this population. The present results further strengthen our hypothesis that the SA gene, or a gene closely linked to this gene, has a capacity to influence blood pressure.