BACKGROUND Lupus anticoagulant (LA) is an autoantibody that inhibits phospholipid-dependent reactions. Studies on the incidence and prevalence of LA in the pediatric population are lacking. The objective of our study was to determine the incidence and potential risk of complications of LA in children presenting with abnormal partial thromboplastin time (PTT). Our secondary objective was to identify signs, symptoms, and medical history associated with the presence of LA as documented in the literature. We focused on the correlation between signs of LA in the form of laboratory values consistent with bleeding abnormalities and the presence of clinical symptoms of bleeding. METHODS We conducted a record-based retrospective analysis of 112 children and adolescents referred to the Department of Hematology/Oncology at Children's Hospital of New Orleans for abnormal coagulation profiles and/or history of mucocutaneous bleeding. Participants were followed up until PTT values normalized. RESULTS In our study population with suspected bleeding disorder, the preliminary incidence of LA was 21%. We found that resolution of LA correlated with correction of PTT in 90% of patients. CONCLUSION To minimize extensive and expensive blood workup, we recommend that screening for LA be included in the evaluation of children with prolonged PTT, even if they have a negative history of bleeding problems.