INTRODUCTION: The purpose of this study was to generate insulin dose (ID) percentiles for children and adolescents with type 1 diabetes mellitus (DM1) having the opportunity to assess this important parameter in relation to age and sex. Individual intensive substitution of insulin is vital for achieving optimum metabolic control in children and adolescents suffering from type 1 diabetes. AIM OF THE STUDY: The aim of this study is: to examine the basic factors which determine daily insulin needs; to establish average insulin doses of the examinees of different ages and sexes and to present them in the form of figures - percentile tables. METHODS: Medical documentation of 100 examinees (55 girls and 45 boys), ages 2-18 were analyzed at the Children's University Hospital in Belgrade in the period between August 1994 and August 2002. All the examinees achieved a satisfactory metabolic control of diabetes after the period of the remission of the disease. The examinees had the conventional insulin therapy (KITh) and intensive therapy (IITh), and they were all using humane insulins. RESULTS: On the basis of the data analysis it has been established that the average insulin dose at ages 3-9 is 0.8 IJ/kg/24h in both sexes, and that from the age of 10 the need for insulin considerably increases with metabolic control deteriorating at the same time. Insulin needs are the greatest during adolescence, especially in girls (1.20 IJ/kg/24h). The ranges of insulin doses show that every child needs an individual approach and estimate of insulin needs. CONCLUSION: It has been concluded that daily insulin needs grow with the growth of chronological age (0.8 before adolescence and 1.16 IJ/kg/24h in adolescence) and that girls get greater insulin doses than boys, especially during adolescence. Insulin needs shown in percentiles (P5 - P95) and presented in the form of figures enable fast and simple visualization of the range of insulin doses at different ages (figures 2 and 3). It is evident that there is a considerable deterioration of metabolic control during adolescence.