Both variety (genotype) and weather (growth-environment components) are accepted as important factors in determining cotton fiber yield. The relationships between cotton genotype and those fiber-quality characteristics considered most important by textile manufacturers have also been examined, and genotypes with potential for producing high yields of fiber with superior spinning properties have been developed. However, just as weather conditions during the growing season reduce fiber yields, the growth environment also alters important fiber-quality characteristics like micronaire and maturity (the fiber properties most closely related to dye-uptake success). Significant genotype-environment interactions further complicate both the maximization of yields and the achievement of cotton fiber properties demanded for modern textile processing. For example, when eight Upland cotton genotypes were grown in South Carolina in 1991 and 1992, fiber-quality quantitation by AFIS showed that genotype was a significant determining factor in fiber length, short fiber content, diameter, circularity, immature fiber fraction, area, fine fiber fraction, micronAFIS, and perimeter. However, growth environment also modified all AFIS fiber properties; and genotype interacted with environment to modify fiber length, short fiber content, circularity, immature fiber fraction and micronaire. When yarns spun from the eight genotype fibers were tested, genotype was a significant factor in yarn nep counts, strength, elongation percent, and breaking tenacity. Environment was a factor in yarn nep counts, uniformity, strength, elongation, and tenacity. Genotype and growth environment were significant factors in dye-uptake success.