Thrombophilic risk factors are associated with thromboembolism in children but data in infants and neonates are not well established. The authors report a series of 9 infants with thrombotic events and the associated genetic risk factors. The clinical and laboratory records of newborns and infants with a history of thrombotic events were summarized, while patients with underlying diseases were excluded. The frequency of the genetic mutations was compared to a control group of 80 children from the same ethnic origin. In 6 patients a cerebrovascular accident was diagnosed and in 3 newborns, CT scan could diagnose antenatal brain infarct. In another 2 patients deep-vein thrombosis associated with femoral catheterization was diagnosed. Seven infants were factor V Leiden heterozygous and another one homozygous. Methylenetetrahydrofolate reductase genotype was found in 5 infants. Five cases were found to be double heterozygous for those two mutations, and another one double heterozygous for FVL and factor II. The results of this small series of patients indicate that cerebrovascular accident is the major thrombotic event in infants and the combination of more than one prothrombotic factors may be the cause of those events. The correct management, including anticoagulant therapy, is still under discussion and waiting for larger series and long-term follow-up results until accurate recommendations can be made.