Stomatal responses to atmospheric change have been well documented through a range of laboratory- and field-based experiments.  Increases in both atmospheric concentrations of CO₂ ([CO₂]) and O₃ ([O₃]) are shown to decrease stomatal conductance for a wide range of species under numerous conditions, although the mechanisms for response vary.  Less well known, however, is whether leaf level responses translate to changes in canopy evapotranspiration (λE).  To address this, maize (Zea mays) was grown in elevated [CO₂] and soybean (Glycine max) in an elevated [CO₂] by elevated [O₃] factorial experiment at the SoyFACE research facility in Urbana, IL.  Canopy λE was measured from canopy closure to senescence using a residual energy balance approach.  This method relies on measures of net radiation, sensible and soil heat fluxes to estimate the energy used for the evaporation of water from canopy surfaces as well as via the transpiration stream.  Both elevated [CO₂] and elevated [O₃] demonstrated decreases in λE for soybean, however, the magnitude of response varied depending on the field season.  The magnitude of response for soybean mimicked the leaf-level data collected at SoyFACE for the three years in which the measurements overlapped.  Elevated [CO₂] also reduced λE for maize and resulted in a greater relative decrease than was observed for soybean.  These types of measurements, while closely linked with leaf-level measurements, are not possible in controlled experiments other than FACE.  The limitations of these measurements and the interpretation of these measurements will be discussed.