Studies were conducted in 2001-2004 evaluating genotype by environment interactions in cotton (Gossypium hirsutum L.). Genotype by Environment interactions were characterized using GGE Biplot for conventional cotton cultivars and their transgenic derivatives. Significant interactions existed for several non-target traits. Transgenic cultivars were taller, had greater height to node ratios, larger seed, and lower lint percentages. Transgenic cultivars containing the Bollgard gene yielded more than their conventional parents and STV4691B was the highest yielding, most stable cultivar. In 2002-2004, GGE Biplot was used to identify two levels (high/low) of discriminating locations for three distinct selection criteria. Crosses were made with parents recommended by a least squares means analysis for each population criteria and F2 plants were planted in the high and low discriminating locations for each population. Gains by selection (h2) were calculated by regressing the F2:3 plants on their F2 parents. Genotypic variance was greater among F2:3 progeny in discriminating environments compared to non-discriminating environments, regardless of population. Heritability was greater in the population containing fiber traits compared to yield. In 2004, GGE Biplot was compared to other widely-accepted stability analysis tools. Correlation coefficients between GGE biplot (stability evaluation) and the Cultivar Superiority Measure, Shukla's Stability Variance, the Eberhart-Russell regression model, Kang's yield stability statistic, and AMMI were 0.54, 0.91, 0.86, 0.63, and 0.55, respectively. Correlation coefficients between GGE biplot (mean performance + stability evaluation) and the Cultivar Superiority Measure, the Eberhart-Russell regression model, Kang's yield stability statistic, and AMMI were 0.95, 0.60, 0.85, and -0.33, respectively. Based on the results of this study and our experience using GGE Biplot, Model 3 with an entry-focused scaling is the most valuable analysis for breeders engaged in cultivar development. GGE Biplot was used with the 1993-2003 Louisiana Official Variety Trials to identify the most desirable (discriminating and representative) test locations in Louisiana for yield and fiber length. St. Joseph loam was ranked 1st for yield, Winnsboro irrigated was ranked 1st for fiber length, and St. Joseph loam was ranked 1st to simultaneously select for both traits. Winnsboro non-irrigated should not be used to select for yield or fiber length.