Thromboembolic events are an increasingly common secondary complication in children who are successfully treated for serious, life-threatening primary diseases. In contrast to adults, thromboembolic events are rare enough in children to hinder clinical trials assessing optimal use of antithrombotic agents. Currently, pediatric patients are treated according to guidelines extrapolated from adults. However, optimal prevention and treatment of thromboembolic events in children likely differs from such treatment for adults. The following review summarizes the available information on commonly used antithrombotic agents in children, which include standard heparin, low molecular heparin, oral anticoagulants, thrombofytic therapy, antiplatetet agents, antithrombin concentrates, and protein C concentrates. The mechanisms, dosing, monitoring, therapeutic range, factors influencing dose-response relationship, and side effects are discussed. Curr Opin Pediatr 1999.11:56–64