Effects of sodium intake on the development of hypertensive vascular lesions were studied in rabbits. Twenty-one animals (group A) were fed a low-sodium diet (7mEq of sodium/day) and 21 animals (group B) were fed a high-sodium diet (28mEq of sodium/day). Hypertension was produced by applying a silver clip (0.9mm in diameter) on the left renal artery. The right kidney was left intact. Animals were killed 7 days after the surgery and hypertensive vascular lesions were examined on microscopic sections. Blood pressure was measured every day and plasma renin activity was measured on the terminal day. The average rise in blood pressure was significantly greater in group B than in group A (p<0.05). The vascular lesions were found in 6 (28.6%) of 21 animals fed on a low-sodium diet (group A) and in 13 (61.9%) of 21 animals fed on a high-sodium diet (group B). The difference in incidence between the 2 groups was statistically significant (p<0.05). However, the presence or absence of the vascular lesions did not always depend upon either the level of blood pressure or plasma renin activity.