Objectives: Studying the prevalence and clinical significance of anti-cardiolipin antibodies in immune thrombocytopenic purpura, as well as in thrombocytopenia with systemic lupus erythromatosus in children.Methods: 20 pediatric SLE patients with thrombocytopenia (Plt <100.000) SLE Cases, 40 pediatric ITP patients, 20 with acute ITP, 20 with chronic ITP, and 20 children representing controls will be selected. From out patient surgical clinic with no history of any hematological or collagen diseases. All patients and controls will be assessed for serum anticardiolipin antibodies (IgG, IgM).Results: Serum levels of anticardipins (Acls) were found in all SLE cases (100%) 17 cases (85%) with positive ACL (IgG). 11 cases (55%) with positive ACL (IgM) In acute ITP, there were 17 cases (85%) had ACLs in their sera, 15 cases (75%) with positive ACL (IgG) and 8 cases (40%) with positive ACL (IgM). In chronic ITP, 17 cases (85%) had ACLs 14 cases (70%) with positive ACL (IgG) and 8 cases (40%) with positive ACL (IgM).