Purpose : To evaluate the usefulness of diffusion weighted MRI (DWI) using the single-shot EPI technique for diagnosis of stroke. Materials and Methods : Conventional Fast Spin Echo T2-weighted MRI (T2WI) and DWI using the single-shot EPI technique were performed in 50 patients with brain infarction. DWI was compared with T2WI according to each stage of infarction studied and apparent diffusion coefficient (ADC) maps showing calculated ADC was aguired. Patients were grouped according to the time interval from symptom onset to MRI performance, as follows : 0 to 6 hours (hyperacute stage, n=3);6 hours to 2 days (acute stage, n=5);3 to 10 days (subacute stage, n=26); more than 11 days (chronic stage, n=16). Results : Hyperacute infarcts were visualized only on DWI. Acute infarcts were visualized on both DWI and T2WI, but were wider and showed more conspicuous signal intensity on DWI than T2WI. At these stages, ADCs of the infarcted area were lower than those of the non-infarcted contralateral side. Subacute and chronic infarcts revealed a relatively equal extent of infarcted area on both T2WI and DWI, and at these stages the ADC of the lesions gradually increased, becoming higher than in the non-infarcted area. In three patients, acute and chronic infarctions were bright on T2WI, but on DWI, acute infarction showed high signal intensity and chronic infarction showed low signal intensity, enabling us to discriminate acute from chronic infarction. Conclusion : DWI using the single-shot EPI technique correctly diagnosed brain infarction, especially the hyperacute stage, and was helpful in discriminating the stage of a lesion.