Antiphospholipid syndrome (APS) is a disease that uncommonly affects children, but when it does, it can have devastating consequences such as strokes or blood clots. New classification criteria for adults with APS have recently been published. Because these criteria consider other factors in an individual’s history beyond clotting, they might lead to earlier diagnosis. They have not, however, been systematically evaluated in children. Through the proposed project, we hope to apply the new 2023 ACR/EULAR Classification Criteria to children seen in pediatric rheumatology clinics to determine how well they predict whether a child has APS. We also hope to study how pediatric rheumatologists are using these new criteria in the real world to make decisions about diagnosis and treatment. The goal is to tailor future research and educational initiatives to fill unmet needs in pediatric APS.