A two-order-magnitude increase in the expression of an endogenous retrovirus was found in myocytes from spontaneously hypertensive rats (SHR) relative to Wistar-Kyoto rats (WKY). It has now been demonstrated that the increase in proviral transcripts is not secondary to the effects of pressure overload, as WKY hearts with hypertrophy due to aortic banding do not express the retrovirus. Crossing SHR with WKY results in intermediate levels of blood pressure, hypertrophy and retroviral gene expression, suggesting co-segregation of genotype and phenotype. Findings suggest a possible linkage between an endogenous retrovirus and genetic hypertension in the SHR. A brief overview of endogenous retroviruses is presented and a discussion of their potential for inducing cardiovascular pathology is considered.