Background. Most age-related changes are associated with the progression of functional instability in organs and tissues. This requires promising definitions of biological age and the pace of the human body development based on laboratory and instrumental assessment of the structure and functions of tissues. The article describes the potential of buccal cells investigations. The purpose was to compare the cytological characteristics of buccal epithelial cells in patients of various age groups (children, young people, the elderly and senile). Methodology. The study of the cytological features of buccal epithelial cells involved patients (men and women) in accordance with the WHO age classification, which were divided into 4 groups. The first group included pediatric patients (under 18 years old, 231 people), the second group included young patients (18―44 years old, 121 people), the 3rd group included elderly patients (60―74 years old, 16 people), and the fourth group included senile patients (75 ―90 years, 5 people). Results. The authors presented buccal epithelium application in non-invasive diagnosis of early human aging; identified common cytological features of buccal epithelium for different ages; revealed the accumulation of cytogenetic abnormalities (epithelial cells with micronuclei, protrusions of the nucleus) and degenerative-dystrophic changes (perinuclear vacuole, condensed chromatin, karyorexis, karyolysis) with age. These findings reflect the predominance of apoptosis over reparation in the process of aging. Conclusions. On this basis, it can be assumed that the buccal cytogram reflects age-dependent processes and can serve as an adequate tool for studying the mechanisms of aging. Among various methods exfoliative cytology is a unique, noninvasive technique involving simple and pain-free collection of intact cells from the oral cavity for microscopic examination.