We conducted an analysis of the body growth pattern of the viviparous lizard Sceloporus grammicus in one of its montane populations in Central México. We calculated 177 individual growth rates for the period comprised between June 1991 and June 1997. Von Bertalanffy growth model provided the best fit to our data in comparison with logistic models. No intersexual differences were found in the growth pattern. The constructed growth curve estimated an age at maturity of 12 and a half months for females and 14 months for males. In spite of marked seasonality in the region, growth rates were not significantly different between seasons. Our results, together with previous studies on the growth ecology of other populations of S. grammicus, suggest that in the volcanic mountains of Central México body growth, and therefore age and size at maturity, are relatively more limited during the whole year in comparison with populations inhabiting northern or lower-altitude localities.