Ischaemic stroke subtypes in children and adults were compared to determine the similarity in aetiologies. Thirty-six children (22 females, 14 males; median age 5 years 7 months, range 6 weeks to 15 years 10 months) and 50 adults (35 males, 15 females; median age 44 years, range 17 years 2 months to 49 years 11 months) who had presented with ischaemic stroke between 1995 and 2000, were categorized using a modified version of the Trial of Org 10172 in Acute Stroke Therapy (TOAST) classification. Proportions of patients in the subtypes of the TOAST classification system were significantly different in the two groups (χ2 test, p<0.01). The first three subtypes (large artery atherosclerosis, cardioembolic, and small vessel disease) accounted for the majority of adult strokes (27 of 50). In contrast, only three of 36 children were accounted for within these three subtypes. The majority of children (29 of 36) were classified within the ‘other determined aetiology’ subtype. Aetiology was undetermined in 12 of 50 adults compared with three of 36 children. Causes of ischaemic stroke in children and adults are distinct. A classification system for ischaemic stroke in children would be useful for collaborative studies.