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We examined life history variation in the lizard, Sceloporus undulatus, across its range. Data from published studies on 14 populations of S. undulatus were analyzed using factor analysis. Four factors were generated from the data. Factor 1 reflected the influence of body size on lizard life histories and explained 31% ofthe variance in S. undulatus life histories. Factor 2 represented the negative relationship of relative clutch mass and number of clutches per year and explained 17% of the variance. The third factor had strong positive loadings of egg mass, age at maturity, and adult survivorship, with a weaker negative loading of the number of eggs per year and explained just over 24% of the variance. The fourth and final factor consisted of strong loading on a single variable, survivorship to maturity, and explained nearly 12% of the variance. Factor 1 was negatively related to Factor 2, but positively related to Factors 3 and 4. Factor 2 was negatively correlated with Factor 4. Factor 2 scores were correlated with the latitude of the study populations; however, no other factor scores were related to latitude, longitude, or altitude of the study populations. Our results suggest that there is an underlying structure to the life histories of S. undulatus that may constrain or limit both local adaptations and proximate environmental effects.