Children and adolescents with type I diabetes mellitus (DM) may present with diabetic ketoacidosis (DKA), which is associated with significant morbidity and mortality. This study aimed to evaluate the hematological parameters at diagnosis (0th hour) and 96th hour after the initiation of treatment in children with DKA. Twenty-six children with DKA treated in Dicle University Faculty of Medicine between September 2002 and August 2003 were included in this study. General characteristics of the patients and hematological parameters (platelet count, white blood cell count, prothrombin time, partial thromboplastin time (PTT), bleeding time, coagulation time, protein C, protein S, antithrombin III, fibrinogen, D-dimer, factor VIII, factor IX, and factor X levels) at diagnosis (0th hour) and 96th hour after the initiation of treatment were determined. The mean age of the children (10 girls and 16 boys) was 9.15 +/- 3.85 years (range: 4-15 years). DKA developed for the first time in 58.3% of these children and they had recently been diagnosed as DM. After hematological parameters at 0th hour were evaluated, increased platelet count, decreased PTT, low protein C, and high factor VIII levels were determined at diagnosis, indicating prothrombotic tendency. If the hematological parameters at 0th hour were compared with those at 96th hour; platelet count decreased, PTT increased, protein C and factor VIII levels turned to be normal at 96th hour. When all the results are considered together, children with DKA appeared to have a prothrombotic tendency. Although this tendency was not reflected in clinical findings in this study, it should be kept in mind that children with DKA are prone to the development of thrombosis and they need to be investigated for the possibility of thrombosis.