In the U.S., Ted Wallace coordinates a Regional Breeders Testing Network (RBTN) for cotton that is sponsored by Cotton Incorporated. The objective of this program is to provide testing sites for public breeders and geneticists across a regional basis. This study looked at various statistical aspects of field testing with emphasis on lint yield. Ten years of data (107 environments) were examined. The objectives were to: 1) determine any relationship between error variance and mean lint yield, 2) establish a procedure for rejecting less precise data, and 3) discern the most optimum testing sites in the program. To achieve the first objective the natural log of error variances were regressed on the natural log of mean environmental lint yields and tested for significance. The "b" value of 0.85 was significant indicating that the error variance increased with increasing yield levels. Using a procedure previously published on rejecting less precise data, the second objective was met. Five of the 107 environments were deemed imprecise and should not have been included in across-location tables. A genotypic index regression method was followed to ascertain the most desirable test sites in the program. Twelve of 23 test sites did an acceptable job of discriminating the entries. Thus, by eliminating nearly half of the test sites more reliable data can be produced, less seed would be required, and more efficient use of resources would be achieved. Sites with less than desirable tests might contribute by collecting data on disease tolerance, morphological traits, or insect resistance, etc. and thus might still be valuable in the cotton RBTN.