Six forms of renin are found in the rat kidney. We studied their secretion in renal slices from spontaneously hypertensive stroke-prone rats (SHRSP) and Wistar-Kyoto rats (WKY). Incubation media from renal slices were subjected to isoelectric focusing. Six peaks of renin activity with different isoelectric points were found. The renin concentration of each form was expressed as a percentage of the total recovered from the gel. We established that the forms secreted by renal slices of SHRSP differed from those of WKY: SHRSP slices released a higher proportion of forms focusing at the more acidic pH. The distribution of the six renin forms and of blood pressure (BP) among animals of the F1, F2, and backcross progenies resulting from the cross of SHRSP and WKY rats were studied. In the F1, BP, percentage of renin form 2, and a combination of the percentage of forms 4 + 5 + 6 were intermediate between the parental lines. The backcross rats showed BP and percentages of forms closer to their SHRSP or WKY parent. In the F2, the distribution of BP, percentage of forms 2 and 4 + 5 + 6 take the form of a unimodal distribution with a significantly larger variance than F1. The increase in the correlation between percentage of renin forms and BP, and between renin concentration of BP, in the segregating progenies over that observed in the parental lines and the F1, are support for the hypothesis that these traits are under the control of common genetic mechanisms.