The effect of cadmium (Cd) on modifications in stomatal structure and function of Cenchrus ciliaris and Cynodon dactylon was investigated to compare the relative Cd tolerance of these 2 grass species. Each grass species from 3 different habitats were subjected to varying levels of Cd, viz., 0, 30 and 60 mg L-1. Growth of all ecotypes of both grasses decreased under Cd stress. A significant reduction in plant biomass, photosynthetic pigments and gas exchange parameters, such as net photosynthetic rate, transpiration rate, stomatal conductance and sub-stomatal CO2 concentration was recorded in all ecotypes of both grass species. Cadmium tolerant populations of both grasses from Pakka Anna relied on water conservation mechanism when exposed to metal contaminated environments. These populations showed high net assimilation rate, low transpiration rate, and high water use efficiency, whereas the anatomical parameters they overexpressed were increased leaf thickness, cortical cell area, conducting tissue area, bulliform area, trichome density, and decrease in stomatal density and area.