In this paper we present data describing whole-plant photosynthetic responses of cotton (Gossypium hirsutum L. cv. Stoneville 825) grown in a controlled environment under nitrogen-deficient and nitrogen-sufficient conditions. After seedling emergence, single plants were irrigated daily in excess to cause drainage with full-strength nutrient solution containing 12 mM of N until the third true leaf was visible. At this time, and in order to expose the cotton plants to nitrogen deficiency, the fritted clay medium in the pots was flushed with 8 L of distilled water and subsequently watered daily with a modified nutrient solution free of nitrogen. Control plants were irrigated daily in excess with the full-strength nutrient solution. Single plants were transferred from a nursery into controlled environment chambers when they reached a leaf area of 0.05 m². Duration of experiments varied from 11 to 13 days. Environmental conditions in the chambers were as follows: air temperature 30 C, dew point 23 C, wind speed 0.6 m s^-1, photosynthetic photon flux density 1500 mmol m^-2s^-1 (at the top of the plant), and outdoor CO₂ concentration. Carbon exchange rates were monitored hourly, whereas leaf area was measured daily. Inhibition of leaf area production and reduction of leaf nitrogen content were primary effects of the limited nitrogen supply. The inhibition of leaf area production resulted in a decreased whole-plant daily rate of gross carbon uptake. The limited nitrogen supply did not affect, however, the rate of gross carbon uptake per unit leaf area, despite nitrogenstressed plants had nearly half of the leaf nitrogen content of the control plants.