Bats roosting in highway bridges in the Trans-Pecos region of Texas and that of south-central Indiana were observed to prefer particular bridges for day-roosts over others with identical construction. The null hypothesis states that both vegetation height and canopy cover were the direct cause of this preference. I sampled general bridge characteristics, vegetation height, transect canopy and cone canopy from 10 occupied bridges and 10 unoccupied (control) bridges from Texas and compared them to 10 occupied bridges from Indiana. Structures were highly variable in size, yet colonial roosts occurred in bridges of all span numbers and variable heights and widths. Vegetation and canopy cover were not significantly different between occupied and unoccupied bridges in Texas (P > 0.05). Vegetation and canopy distribution between Indiana and Texas occupied bridges did not show a pattern. These factors were also similar between occupied sites and controls in Texas, indicating that other factors are involved in attracting bats to bridges. Emergence behavior and vegetation data show the Mexican free-tail bat (Tadarida brasiliensis ) emerged toward less vegetation, whereas the big brown bat ( Eptesicus fuscus) emerged toward greater vegetation. Emergence counts were performed on each bridge to estimate population numbers and to indicate a correlation between direction of emergence and vegetation height. This study shows the insignificance of vegetation and canopy in roost choice. Temperature and structure construction are presumed to be factors with greater influence on roost choice.