Abstract: Three groups of adult stroke-prone spontaneously hypertensive rats(SHRsp) were treated with m-nifedipine(m-Nif)2. 5, 5 and 10 mg ·kg^-1 byintraperitoneal injection. The systolic blood pressure (SBp) decreased significantly. Thehypotensive effect persisted for 2 ～4,6 ～8, and 12 h respectively and the peak effect ap-peared in 1 h. The range of hypotension was markedly greater than that of nifedipine(Nif). In SHPsp, treatment with m -Nif 10 or 30 mg·kg^-1·d^-1 for 4 weeks reducedsignificantly the SBp, but the hypotensive action is about the same as Nif.