Cotton varieties develop differently because they present different physiological characteristics in production environments. This study aimed to know the physiological characteristics of cotton. The experiment was carried out at the São Paulo Agribusiness Technology Agency (APTA), Alta Paulista region. The experimental design used was Entirely Randomized (DIC), with six cotton cultivars: IMA5801B2RF; FM975WS; TMG47B2RF; TMG81WS; FM944GL and IACRDN. Where the following physiological parameters were determined: Assimilation rate CO2, leaf transpiration, stomatal conductance, internal concentration of CO2 in the substomatic chamber and efficient use of water. The cotton varieties showed different physiological characteristics, the IMA5801B2RF variety had the lowest performance, which may reflect low productivity. Further physiological studies are needed to understand the Cotton varieties behavior