Stomatal conductance potential is correlated with heat tolerance in Pima cotton (Gossypium barbadense L.) . This study was conducted to determine the inheritance of stomatal conductance and the potential for its increase in elite Pima strains. Crosses were made between an obsolete cultivar, Pima 32, a modern cultivar, Pima S-6, and an elite strain, P73. Populations were produced for the F₁, F₂, and backcross generations. In 1992, the populations of each cross were grown in five randomized blocks at Maricopa, AZ. Stomatal conductance measurements were made between 1400 and 1600 h each day the time of maximum phenotype differentiation. Broad sense heritability estimates of the crosses PS-6 x Pima 32, P73 x Pima 32, and PS-6 x P73 were 0.438, 0.322, and 0.405, respectively. Preliminary data from scaling tests indicated that the cross PS-6 x Pima 32 could be described adequately by a simple additive-dominance gene action model. Additivity was the only significant parameter operating in the above cross. In the P73 x Pima 32 cross, in addition to simple additive and dominance gene action, both additive x additive and dominance x dominance epistatic interactions were present. In the cross PS-6 x P73, all gene action parameters were significant. The small size of the additive parameter and the negative sign of the dominance parameter suggested that selective advance for higher conductance would be limited in the above cross.