Background:Intravenous tissue plasminogen activator (IV tPA) has been studied primarily in patients over age 50. We sought to describe baseline differences in adult patients ≤50 years-old taken from a large prospective cohort of acute stroke patients treated with intravenous tPA (IV tPA) and to determine whether outcomes differed for this population.Methods:Data (n = 1120) prospectively collected from the Canadian Alteplase for Stroke Effectiveness Study (CASES) were reviewed and patients aged ≤50 years-old (n=99) were compared with those aged >50 years (n=1021) with regards to baseline characteristics, symptomatic intracerebral haemorrhage (sICH), functional outcome at 90 days and death.Results:Nine percent of patients were ≤50 years-old. Among patients aged ≤50 years, 40.4% were women and median age was 42 ± 6.1 years (range 20 to 50). They had significantly more current cigarette use but fewer other vascular risk factors than older patients (p<0.05) and their baseline median NIHSS score was lower (13 versus 15, P=0.001). Although this group was more likely to have a favourable 90-day outcome, multivariable regression confirmed that age ≤50 years, while independently associated with a decreased risk of death (RR 0.36, 95% CI 0.14 to 0.95), was not itself predictive of favourable 90-day outcome or decreased risk of sICH.Conclusions:Adult patients ≤50 years-old had fewer medical co-morbidities and a modestly lower baseline median NIHSS score than their older counterparts. Age ≤50 years was independently associated with a decreased risk of death but not with favourable outcome or risk of sICH.