Available literature on the gross carbon dioxide exchange rates of Pima cotton canopies grown under variable temperatures and CO₂ enriched environments is limited. Pima cotton (Gossipium barbadense L., cv. S-6) was reared in pots under natural environmental condition at the nursery site located at the USDA/ARS, Crop Simulation Research Unit, Mississippi State University, MS. At first bloom nine plants were moved into six naturally lit plant growth chambers maintained at day/night temperatures of 25/17, 30/22, and 35/27 C and CO₂ of 350 and 700 uL L^-1. Hyperbolic light-response curves were employed to characterize the photosynthetic response in all canopies. The temporal trends in quantum efficiency ranged from 1.1 to 11.5 ug CO₂ umol^-1 photons, whereas the conductance to CO₂ transfer ranged from 1.1 to 24.3 mm s^-1 for all cotton canopies studied.