An agent for prevention or treatment of vascular disease and renal dysfunction that are accompanied by the migration of vascular smooth muscle cells and mesangial cells comprises as an active ingredient a growth-hormone secretion promoting substance receptor agonist that have a strong inhibitory action on the migration of vascular smooth muscle cells and mesangial cells. Using such an agent for prevention or treatment, one can suppress arteriosclerosis, recurrence of intimal thickening after angioplasty, and even glomerulosclerosis.