Several genetic loci involved in blood pressure regulation have recently been localized in experimental models of hypertension, but the manner in which they influence blood pressure remains unknown. Here, we report a study of the Lyon hypertensive rat strain showing that different loci are involved in the regulation of steady-state (diastolic pressure) and pulsatile (systolic-diastolic, or pulse pressure) components of blood pressure. Significant linkage was established between diastolic blood pressure and a microsatellite marker of the renin gene (REN) on rat chromosome 13, and between pulse pressure and the carboxypeptidase B gene (CPB) on chromosome 2. These findings show that two independent loci influence different haemodynamic components of blood pressure, and that pulse pressure has a specific genetic determination.