Current epidemiological data suggest that strokes are occurring at a younger age. As many as 1 out of every 6 strokes occurs in a young adult (18 to 50 years old). Heterogeneity in incidence rates, stroke subtypes, and etiology among younger stroke victims in both developed and developing countries is often noted. Certain historical features and clinical manifestations may occasionally serve as clues toward specific stroke etiologies; nevertheless, determination of etiology, particularly of ischemic stroke in the young, poses many challenges due to a broad array of potential causes, both common and uncommon. In this article, the authors emphasize areas in which the differential diagnosis of stroke and etiologies (including those in pregnancy and puerperium) differs from that in older adults. The authors also note relevant information concerning prognosis of young adults with stroke.