The effects of MPC-1304, a newly developed 1,4-dihydropyridine derivative, on blood pressure and hypertensive complications in stroke-prone spontaneously hypertensive rats fed a high-salt diet (0.8% NaCl), were investigated. The antihypertensive effectiveness of nicardipine was used for the purpose of comparison. MPC-1304 and nicardipine were added to the diet, in doses of 0.01% (0.01% MPC-1304 diet), 0.03% (0.03% MPC-1304 diet) and 0.1% (0.1% nicardipine diet), respectively, throughout the experimental period (8 to 30 weeks of age). This chronic ingestion of MPC-1304 and nicardipine inhibited the development of hypertension and reduced the concentration of blood urea nitrogen, creatinine, triglyceride and total cholesterol in serum. Treatment with MPC-1304 inhibited the incidence of cerebral stroke, cardiac fibrosis, proliferative and fibrinoid arteriolitis and malignant nephrosclerosis. There was no significant difference in the antihypertensive effectiveness between 0.01% MPC-1304 and 0.1% nicardipine diets. Thus, MPC-1304 had antihypertensive effects in stroke-prone spontaneously hypertensive rats.