We describe two previously healthy children who had multiple ecchymoses several days after acute infection. In both cases, the prothrombin time (PT) and the activated partial thromboplastin time (APTT) were prolonged. Further examinations revealed the presence of lupus anticoagulant (LA), phosphatidylserine-dependent antiprothrombin antibodies (aPS/PT), and low serum complement. In both cases, we confirmed the presence of a serum immune complex. The patients' symptoms improved spontaneously within 1 week, and all laboratory data normalized within several months. We also describe another asymptomatic case positive for LA and aPS/PT presumably associated with cytomegalovirus infection. The prevalence of transient antiphospholipid antibodies associated with viral infections in children must be much higher than we expected. We have to take it into consideration when we see abnormal coagulation results, but the occurrence of significant bleeding symptoms is rare.