Two wild cotton lines respond differently to environmental stress. While T25 leaves remain very turgid even under extreme environmental stress, T169 leaves wilt dramatically (1). The objective of our research was to determine if this response is related to changes in the pattern of call wall protein synthesis during stress. The two lines were grown in irrigated and nonirrigated field environments. The first unfolded leaf and the third and fifth leaves distal to the shoot moriatem were harvested and the cell wall proteins then extracted by infiltration with sucrose or CaCl₂. Amino acid analysis of the insoluble cell wall fraction showed hydroxyproline to be the only amino acid affected by both stress and stage of leaf development. Under dryland conditions, the level of hydroxyproline was much lower in T169 than T25, whereas the level was much higher in T169 in irrigated samples. Gel electrophoresis, followed by silver staining, revealed both qualitative and quantitative changes in cell wall proteins between stages of leaf development and between cotton lines. Two proteins were unique to T25 and were synthesized only under dryland conditions. In addition, six proteins were unique to T169 and these were also found only under dryland conditions. One of the major limitations for growth under conditions of environmental stress is cell wall expansion which may be affected by such changes in cell wall proteins.