Kidney weight, renal renin content, and blood pressure were measured in rats with different degrees of renal ischaemia induced either by means of a clip on one renal artery or by stenosing the aorta between the origins of the two renal arteries, the ureter of the ischaemic kidney left free or being ligated. Renal ischaemia was more pronounced after aortic constriction than after clamping the renal artery, and renin production was more stimulated in the first case. In the ischaemic kidney a negative correlation between renal mass and renin content was found, but renin content of the kidneys was not correlated with the degree of hypertension .