AbstractIn Squamates, head meristic characters are commonly used in analyses of intraspecific variability, systematics and phylogeny. Taxonomic significance of head scales is based on the assumption that discrete values of particular scales are set at birth and stable during individual ontogeny. In this paper, we analysed ontogenic changes of head scalation in a population of meadow viper (Vipera ursinii), based on multiple recaptures of marked individuals. Our results show that changes of cephalic scales occur both in immatures and in adults; the frequency of occurrence of change in the sample of re-photographed individuals was 52.2%. Oligomerisation was the most frequent change, found in 39.1% of re-photographed individuals. Changes in shape of cephalic plates as well as polymerisation were recorded in 30.4% of re-photographed individuals. Results of the log-linear analyses indicated no relation either between scale change and sex or between scale change and growth. Although we do not suggest that meristic characters of head scales are completely inadequate for taxonomic use, we point out the need for taking into account the ontogenic trajectories of these characters when analysing intra- and interpopulation variability, in systematics and phylogeny.