While studying the cytogenetic status of human cells following the exposure to genotoxic factors it is necessary to know the baseline values of the studied parameters. The value of the spontaneous frequency of cells with micronuclei is an important starting point in performing both the biomonitoring of the human populations and fundamental research, connected with the investigation of the mechanisms of the chromosome aberrations. The objective of this study was to analyze the frequency of T-lymphocytes with micronuclei depending on the age in residents of the Southern Ural who were not affected by accidental exposure. The study was performed using the micronucleus assay, the peripheral blood lymphocytes were cultured with FHA and cytochalasin B. The study group consisted of women and men aged 18–82 whose working and living conditions are not connected with hazardous industry. For the first time, the age-related characteristics of the frequency distribution of lymphocytes with micronuclei among the population of the Southern Urals in different age groups are presented. It was found that the frequency of lymphocytes with micronuclei increases monotonically with age up to the age of 50–70 years. After that it does not change much. No statistically significant sex-dependent differences in the baseline values of the cells with micronuclei were observed. However, women have larger data spread.