Objective. To determine the peculiarities of sexual development in the adolescents with type 1 diabetes mellitus (DM1).Materials and methods. The puberty pattern was assessed in 52 boys and 64 girls aged 9 to 17 years with DM1 with the disease duration of 1 to 8 years. Sexual development was evaluated according to Tanner using the masculinization index for boys and secondary gender score for girls. The puberty pattern was determined taking into account age standards. Carbohydrate metabolism compensation was assessed by the levels of glycosylated hemoglobin (Hb A1c): values < 6.05 % were defined as ideal compensation level, Hb A1c of 6.05 % — 7.5 % as optimal; values 7.6 %—9.0 % as suboptimal and Hb A1c > 9.0 % was assessed as a high risk for life. The analysis of puberty pattern was carried with account of the age of DM1 manifestation and disease course duration, and compensation of carbohydrate metabolism. Depending on the age of DM1 manifestation, four groups were defined: group 1-at the age of 1 to 8 years, group 2-at 9 — 10 years, group 3-at 11 — 13 years, groups 4 included patients with manifestation later than at 13 years. Based on the DM1 duration, three groups were determined: group I — up to 5 years; group II — from 5 to 10 years; group III-more than 10 years.Results. The evidence has been obtained for the negative DM1 effects on the course of sexual development and formation of the menstrual function. In boys with DM1, which manifested in childhood and prepuberty, there was a later onset of puberty and prolongation of the external genitalia development. The DM1 girls demonstrated a delayed menarche age (13 years 1 month ± 1.7 month) in comparison with the mean menarche age (12 years 9 months ± 1 month). In 38.1 % of female patients, menstrual disorders were diagnosed, mainly in a form of oligomenorrhea and secondary amenorrhea. The delay in sexual development was established in 10.5 % of boys and a 7.5 % of girls, the formation of which was negatively affected by the age of manifestation of type 1 diabetes in children and prepubertal age and unsatisfactory compensation of carbohydrate metabolism.Conclusions. Patients with the onset of diabetes mellitus 1 in childhood and prepuberty with insufficient compensation of carbohydrate metabolism refer to the group with the risk of puberty disorders.