Since cool temperatures occur in late-September and October when harvest aids are usually applied in the Southern Rolling Plains of Texas, tests were conducted to determine the response of cotton conditioners, defoliants, and desiccants under cooler environmental conditions. From 1992 through 1997, twenty-five different harvest aid chemicals have been used in 24 replicated small plot and nine large block tests. In these tests, 190 different harvest aid treatments have been evaluated. The harvest aids were applied alone or in combinations with other harvest aids and/or adjuvants. In these tests, the use of harvest aids generally resulted in increased leaf defoliation and desiccation. However, environmental conditions, maturity of the crop, variety of cotton and the management of soil moisture and nutrients are important variables that impact the performance of the harvest aid materials applied.