PURPOSE: Status epilepticus (SE) is an uncommon but potentially life-threatening seizure. It is most common in children. Little is known about the differences within the pediatric age group in terms of the type of patient seen with SE. METHODS: We analyzed the records of 394 children aged 1 month to 16 years who were part of two large studies of pediatric SE conducted in Bronx, New York, and Richmond, Virginia. The 394 children had a mean age of 4.4 years and included 349 (89%) with an initial episode of SE. RESULTS: Status epilepticus was most common in younger children with >40% of cases occurring in those younger than 2 years. The distribution of causes was highly age dependent. More than 80% of children younger than 2 years had SE of febrile or acute symptomatic origin, whereas cryptogenic and remote symptomatic causes were most common in older children (p < 0.001). One hundred fifty-eight (40%) of the cases were known to be previously neurologically abnormal, including 35 (21%) of 169 younger than age 2 years and 123 (55%) of 225 older than 2 years (p < 0.001). One hundred seventy-seven (45%) children had a history of seizures including 142 (41%) of the 349 children with a first episode of SE. A history of seizures was present in 34 (20%) of those younger than 2 years and 143 (64%) of those older than 2 years (p < 0.001). The effect of age remained significant even when the analysis was limited to those with SE of cryptogenic or remote symptomatic origin. CONCLUSIONS: There is a strong effect of age on the frequency and etiology of SE, as well as on the type of child who has SE. In young children, SE occurs primarily in children who are neurologically normal and with no history of unprovoked seizures. In older children, SE occurs primarily in those who are known to have prior unprovoked seizures and who are often also neurologically abnormal.