Dental polymorphism in a population of the red fox Vulpes vulpes (L.) from Poland was studied in a sample of 1453 specimens (637 males, 535 females and 281 specimens of unknown sex). Frequency distributions in 15 groups of morphotypes (A–O) were analysed and a pattern of qualitative features was constructed on the ground of frequency analysis of particular morphotypes. An increase in complication of tooth shape of the carnassial region (P4, P4, M1, M1), as well as higher morphological variation of the teeth from borders of the cheek rows (P1, P1, M2, M3) were ascertained. Almost all groups of morphotypes, excluding three, presented absence of significant sexual differences. The pattern of qualitative features was used to verify an existing model of genetic control of evolutionary changes in dental morphology of mammals. Positive, statistically significant relationships between the dental size and presence or degree of formation of the dental structures confirmed the operation of the size-related mechanism, i.e. threshold mechanism, during ontogeny.