Four hundred and twenty-five reproductive-aged women were examined to study the specific features of menstrual function in patients with type 1 diabetes mellitus (DM). Group 1 included 211 patients with type 1 DM onset before menarche; Group 2 comprised 214 patients who had developed DM after menarche. General clinical, biochemical, hormonal, and statistical studies were performed. The patients with type 1 DM were ascertained to develop menstrual dysfunction more frequently if the onset of DM occurred before menarche and if they had a longer history of the disease. There is a direct relationship between the prevalence of menstrual irregularities and the degree of DM compensation. The significant preponderance of late vascular complications of DM was found in the patients with its onset before menarche.