Abstract: AIM: To study the therapeutic effects of L-lysine monohydrochloride(LMH) on focal cerebral ischemia in rats. METHODS: Focal cerebral ischemia was produced by permanent occlusion of the proximal portion of the right middle cerebral artery (MCA) according to the technique of Tamura. The infarct area was measured by 2,3,5-triphenyltetrazolium chloride (TTC) staining technique. The extent of neurological deficits was evaluated by the method of Bederson. The histological neuronal changes after middle cerebral artery occlusion(MCAO)in rats were also studied. RESULTS: LMH(621.5 and 310.8 mg.kg^-1, ip) was shown to be able to decrease significantly the infarct area(from 18.00%±5.67% in control to 8.46%±3.01% and 10.91%±6.17% in LMH treated groups) and the numbers of neurons which were degenerated and necrotic in the related cerebral regions(from 57.9%±10.9% in control to 31.9%±4.8% and 36.8%±10.0% in LMH treated groups) 24 h after MCAO. LMH(621.5 mg.kg^-1, ip) also markedly ameliorated the neurologic deficits score of rats. CONCLUSION: LMH has protective effects on cerebral ischemia.