We investigated the efficacy of edaravone in patients with cardioembolic stroke. Cardioembolic stroke patients were treated with drip intravenous infusion of edaravone (ED group, n=141) for 7 days, and were retrospectively compared with a historical-controlled cohort of similar patients (control group, n=114). Early improvement (between day 0 and day 10), defined as change in National Institutes of Health Stroke Scale (NIHSS), was seen more frequently in mild patients (NIHSS on admission < or = 7) among the ED group than in the control group (change in NIHSS +2 vs. -2, respectively, p=0.013). Similar efficacy was not seen in the moderate to severe (NIHSS >7) patients. Independent patients (modified Rankin Scale < or = 2) 6 months after the onset were likely to be less frequent in the ED than the control group (28% versus 41%; p=0.066). Other clinical outcomes in the ED group were not significantly different from those in the control group. The results suggest that edaravone may only be effective in mild patients with cardioembolic stroke.