The utility of measurements such as chlorophyll fluorescence, CO2 and O2 exchange rate, stomatal conductance, internal CO2 concentration and electron transport rate have been evaluated as possible tools in the determination of drought tolerance among cotton cultivars. A greenhouse experiment was established containing two cotton cultivars: one termed drought tolerant and one termed drought susceptible. The design of the experiment was a split plot with the two cultivars as main plots and two dry periods as subplots. The first dry period was initiated at the 4th node growth stage and the second at early bloom. The findings of the above experiment will be discussed in this paper.