Information regarding stroke in the younger patient population first began appearing in the literature in the 1950s and 1960s. Interest in this topic has increased due to escalating stroke rates in the younger age group and improvements in patient evaluation. A standardized definition of “young adults” is lacking. People under 40, 45, 50, or even 55 years of age have been classified as young adults. Currently, strokes occurring after adolescence and before the age of 50 are typically considered as occurring in young adults. Although several of the causes of stroke in the young are rare, they account in aggregate for many of the conditions leading to stroke (Kristensen et al 1997; Martin et al 1997; Kittner et al 1998). The incidence of stroke increases sharply after the age of 40, and the spectrum of etiology narrows, with atherosclerosis becoming increasingly common as the risk factors start resembling those in the elderly.