Fluctuations in cotton (Gossypium hirsutum, L.) yield in the Tennessee Valley of Alabama are common and usually related to drought or irregular rainfall. A sprinkler irrigation study was established from 1999 to 2004 to evaluate the minimum design flow rate to produce optimum cotton yields and economic gain. A replicated randomized block design consisting of four irrigation treatments ranging from one inch every 12.5 days (equivalent to 1.5 gpm acre-1 design flow rate or system capability) to one inch every 3.1 days (6.0 gpm acre-1) and a control, rainfed treatment. Daily plant water requirement was determined using soil moisture sensors and a spreadsheet-based scheduling program (MOISCOT) developed by Alabama Cooperative Extension engineers. Significant yield differences between irrigated and rainfed cotton were noted during the study period, with rainfall variability and treatment effects accounting for most of the yield response.