PURPOSE: Although von Willebrand disease is the most frequent hereditary hemorrhagic disorder. Its biological characteristics make some difficulties in diagnosing this common disease, so careful individual history taking and laboratory evaluations for this disease are important as the patient who has a bleeding tendency may show normal values on screening tests. We performed this study to evaluate the clinical aspects of von Willebrand disease. METHODS: Eighteen cases were diagnosed as von Willebrand disease at the Department of Pediatrics, Kyungpook National University School of Medicine, Taegu, Korea from February, 1996 to June, 1998. We performed screening tests and specific tests for coagulation on these patients and reviewed their past and family histories. RESULTS: Thirteen boys and five girls were diagnosed and their mean age was 7.1 years (range: 0.5~17.7 years). Seventeen cases showed prolongation of activated partial thromboplastin time, only one case which had immune thrombocytopenic purpura showed lower than normal platelet count. Fourteen cases had lower than normal range factor VIII concentrations. Thirteen cases of vWF related antigen and twelve cases of vWF ristocetin cofactor had low values. In sixteen cases which were tested their ABO blood-group were divided into three groups, group A included four cases, group B included three cases and O group included nine cases. Family history of this disease was positive in three cases, in two cases they were sister and brother and in one case his mother was also diagnosed as von Willebrand disease. Three cases had congenital heart disease concomitantly. CONCLUSION: von Willebrand disease is a common hereditary disease but the diagnosis of this disease remains a clinical problem from several aspects, therefore we should consider von Willebrand disease when we evaluate the patient who has a bleeding tendency. This may help us to manage and to prevent accidental bleeding episodes in von Willebrand disease patients.