Measurements of CO₂ and H₂O fluxes of crop plants are essential to understanding the impacts of environmental variables on crop productivity.  A portable, CETA (Canopy Evapo-Transpiration and Assimilation) chamber system was built and evaluated at Big Spring, TX.  This chamber system is an open or flow-through system that, once field deployed, can operate unattended for extended periods. To characterize the performance of these chambers under field conditions, six identical chambers were constructed and tested in the field on subsurface drip irrigated cotton in Lubbock, TX.  In addition to quantifying the degree of crop drought stress in terms of canopy gas exchanges we also compared CETA responses with simultaneous leaf-level gas exchanges made with two automated LI-6400 portable photosynthesis systems.