The study presents the comparative analysis of scabies and STI incidence in different groups of population in Saratov region from 1991 till 2010. Principal causes and factors supporting epidemic process of infectious diseases in this region on an extent of 2 decades are revealed. It is established that if the basic group patients with scabies were children, teenagers and people at the age from 20 to 29 years, so, in the group with STI there were patients aged from 18 to 29 years. Besides, it was proved that over the last years early and late latent forms of syphilis and neurosyphilis prevail among patients in age group from 40 to 60 years. It leads to disability, and sometimes invalidism quite often.