The objective of this study was to evaluate the underlying diseases, thrombus localization, and other risk factors in pediatric patients with recurrent thrombosis in order to obtain a sense of early awareness of the possible recurrences. We retrospectively evaluated both inherited and acquired thrombophilic risk factors in children with recurrent thrombosis that were diagnosed and treated at Hacettepe University, School of Medicine, Department of Pediatric Hematology, Ankara, Turkey. Both congenital and acquired risk factors associated with recurrent thrombosis, and treatment modalities were analyzed in detail. Among 569 children with thrombosis, 32 (5.6%) presented with recurrent thrombosis. Median age at first presentation in these 32 patients [11 women (34.4%) and 21 men (65.6%)] was 132 months. In all, 29 (90.6%) of the 32 patients had an underlying chronic disorder: the most common of which was congenital heart disease [n=11 (34.4%)]. At presentation intracardiac localization, including the entrance of the inferior and superior vena cava, was observed in 10 of the patients (31.2%). Thrombosis recurred at the same location in 15 (47%) patients and at a different location in 17 (53%). Median time interval between the first and second episode of thrombosis was 6.5 months (range: 1-180 months). Considering both acquired and congenital thrombophilic factors, three (9.3%) patients, four (12.5%) patients, and 14 (43.8%) patients had five, four, and three risk factors, respectively. More than half of the patients had elevated plasma FVIII (>150 IU/dl) and D-dimer (>0.5 mg/ml) levels. Thrombectomy was performed in three patients with organized, chronic intracardiac thrombus. Tissue plasminogen activator (t-PA) was used more frequently to treat recurrence than the first event (15.6 vs. 28.1%) and consequently the complete resolution rate was higher (40 vs. 77.7%) at the second event. Thrombi partially resolved in 11 of the patients during the initial episode and in 10 patients during recurrence (34 vs. 32%). In all, 29 (87.5%) patients were using prophylaxis at the time of recurrence. [coumadin (n=16), low molecular weight heparin (n=12) and aspirin (n=1)]. In total, four patients (12.5%) died because of their underlying disorders and six (18.7%) developed postthrombotic syndrome during the follow-up. Recurrent thrombosis should be expected, especially in cases with congenital heart disease, incomplete thrombus resolution, and elevated plasma FVIII/D-dimer levels. In the light of this knowledge we suggest aggressive treatment for pediatric patients with a high risk of recurrent thrombosis. Blood Coagul Fibrinolysis 23:434-439 (C) 2012 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.