The term "minor stroke" is often used; however a consensus definition is lacking. We explored the relationship of 6 "minor stroke" definitions and outcome and tested their validity in subgroups of patients. A total of 760 consecutive patients with acute ischemic strokes were classified according to the following definitions: A, score < or = 1 on every National Institutes of Health Stroke Scale (NIHSS) item and normal consciousness; B, lacunar-like syndrome; C, motor deficits with or without sensory deficits; D, NIHSS < or = 9 excluding those with aphasia, neglect, or decreased consciousness; E, NIHSS < or = 9; and F, NIHSS < or = 3. Short-term outcome was considered favorable when patients were discharged home, and favorable medium-term outcome was defined as a modified Rankin Scale score of < or = 2 at 3 months. The following subgroup analyses were performed by definition: sex, age, anterior versus posterior and right versus left hemispheric stroke, and early (0 to 6 hours) versus late admission (6 to 24 hours) to the hospital. Short-term and medium-term outcomes were most favorable in patients with definition A (74% and 90%, respectively) and F (71% and 90%, respectively). Patients with definition C and anterior circulation strokes were more likely to be discharged home than patients with posterior circulation strokes (P=0.021). The medium-term outcome of older patients with definition E was less favorable compared with the outcome of younger ones (P=0.001), whereas patients with definition A, D, and F did not show different outcomes in any subgroup. Patients fulfilling definition A and F had best short-term and medium-term outcomes. They would be best suited to the definition of "minor stroke."