The long term effects of amlodipine, a new long acting Ca2+ channel antagonist on organ damage, stroke and life span, were examined in stroke prone spontaneously hypertensive rats (SHRSPs). Blood pressure of the SHRSPs increased over the first 16 weeks and reached a stable level of about 250 mmHg in controls and about 200 mmHg in the amlodipine treated group. At 15 weeks after starting amlodipine treatment, all control SHRSPs exhibited varying degrees of myocardial fibrosis, proliferative and/or necrotic vasculitis and glomerular lesions, whereas only a few animals in the amlodipine group showed slight lesions. The average life span of animals was estimated to be 43.3 weeks and 71.1 weeks for control and amlodipine groups, respectively, which suggested a 1.6-fold prolongation of their life span by amlodipine treatment. These results indicate that the long term treatment of amlodipine suppresses the incidence of organ damage and stroke in SHRSPs and prolongs their life span.