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Along the international border separating the U.S. (Arizona) and Mexico (Sonora), differences in the grazing intensity of domestic livestock are commonly presumed to have created a large difference in vegetation cover between the two countries. This vegetation difference is reportedly responsible for an extensive albedo and temperature discontinuity that may be affecting regional climate. In this study, we used Landsat Thematic Mapper data to examine trans-border differences in these two biophysical parameters. Albedo and radiant temperature estimates were computed for 25 km-long (east-west) transects through semi-desert grassland on each side of the border at two different times of year. Only small average trans-border differences in these parameters were found, and in some cases average albedo and temperature data were essentially equal on each side of the border. In addition, we found significant spatial heterogeneity in conditions on both sides of the border. These results suggest that, based on a small sample, it may be difficult to assess whether there are significant differences in biophysical properties of semi-arid grassland between Arizona and Mexico in the vicinity of the border. We conclude that more extensive spatial and temporal sampling is critical in assessing any possible trans-border differences in average terrain conditions that might affect climate, and that this data must be coupled with more extensive meteorological data to assess whether a difference in climate also exists.