Thromboembolism (TE) has recently been recognized as a clinical entity in children. Determining the clinical characteristics of pediatric TE is an important first step in dealing with this new disorder. The paper summarizes 1776 consecutive children with systemic TE referred to 1-800-NO-CLOTS telephone consultation service. 1-800-NO-CLOTS is a free consultation service for clinicians managing pediatric TE. Patient information was collected immediately using standardized forms. In children with systemic TE, infants under one year of age (47%) including neonates (26%) represented the largest distinct pediatric age group. Age-related differences were seen in TE locations, associated conditions, and risk factors. However, venous TE was the most frequent manifestation (74%). Neonates and children with cardiac disorders were more likely to have an arterial TE than a venous TE Beyond the neonatal period, venous TE associated with a central line is more likely to occur than arterial TE. Children with ALL were 5.7 times more likely to have a venous TE than an arterial TE. TE were infrequent in otherwise healthy children with 90% of children having at least one risk factor. Central catheters were the single most common risk factor associated with TE, present in 2/3 of children. Ultrasound was most frequently employed for diagnosis of TE. Finally, there was marked heterogeneity in treatment of children with TE. In children, neonates form the largest single group with TE. TE usually occur only in the presence of one or more risk factors with catheters being the single most important factor.