High temperature stress adversely affects cotton growth and development. This paper presents preliminary results of studies evaluating methodologies that measure the ability of cotton to tolerate high temperatures. Simple methodologies that measure cell damage and loss of enzymatic function are being employed to measure the tolerance of cotton cultivars to high temperatures. Early results suggest that there is some variation among cultivars in their ability to withstand high temperatures under laboratory conditions. These methodologies will be further evaluated to establish their value in identifying thermotolerant cotton cultivars for potential use in cotton breeding programs