ObjectiveMagnetic resonance imaging (MRI) was used to investigate the therapeutic effects of imidapril, a newly synthesized angiotensin converting enzyme (ACE) inhibitor, on cerebral stroke lesions.DesignPretreatment with ACE inhibitors is known to prevent stroke in stroke-prone spontaneously hypertensive rats, prolonging their lifespan. Malignant stroke-prone spontaneously hypertensive rats (M-SHRSP) were treated with imidapril after the onset of stroke.MethodsM-SHRSP with proved stroke were divided into two groups. One group received 40mg/kg per day imidapril and the other group was used as a control. For 4 weeks, neurological symptoms were scored daily, and MRI images were taken and scored once a week.ResultsIn the control group the MRI score for cerebral lesions increased during the experiment, and seven out of eight control rats died within 17 days. In rats treated with imidapril the major finding was that imidapril rapidly ameliorated the damage to the blood-brain barrier and resolved brain oedema within 1 week. At the same time the neurological symptoms observed after stroke disappeared. Furthermore, none of the rats treated with imidapril showed recurrence of stroke, and their survival rate was improved.ConclusionThese results suggest that imidapril has therapeutic effects on stroke lesions, as well as prophylactic effects on the recurrence of stroke.