Multiple factor analysis was used to interpret geographical variation of gene frequencies. Allelic frequencies at three loci (two esterase loci, Esr and Esh, and a malic dehydrogenase locus) from ants (Pogonomyrmex barbatus) collected throughout Texas and reported by Johnson et al. (1969) were reexamined for patterns of correlation with five environmental measurements: mean January temperature, mean July temperature, mean annual precipitation, elevation, and annual growing season. These measurements and the associated gene frequencies at each sampling location were subjected to factor analysis. Variables highly correlated with the same factor were hypothesized to be causally related.