The method of intracellular microelectrophoresis in the form of EMN (Electrophoretic Mobility of Cell Nuclei) index can assess well the biological process of human aging in the course of ontogenesis. The aim of this study is to present an application of EMN index as a measure of the biological process of human aging in Maja Indian population from Yaxcaba village (Yucatan, Mexico). The percentage of EMN index is calculated on the basis of the number of epithelial cells with mobile nuclei in reference to the cells with immobile nuclei per 100 cells counted by the researcher. Electrophoresis is performed using a special Biotest apparatus. In the examined (439 females and 337 males) a marked decrease of average values of EMN index was observed. Lower mean EMN value in females is observed. Confirmation of these negative tendency are the simple regression lines in the stable and involutional phases of the ontogenesis for males and females. The EMN index correlate negative with age (statistically significant p0,01) for males r = -0,28 and for females r = -0,35. It follows that the EMN index is a good criterion for assessment in biological process of aging (assessment of biological age). The collected material needs further studies.