Under the general agreement that growth environment significantly affects cotton fiber yield, breeders and agronomists have collaborated to maximize fiber yield over a wide range of growth conditions. Growers also accept the concept that fiber properties such as micronaire and maturity are modified by the environment in which the fiber is produced. However, the nature and levels of these modifications are difficult to quantify, and the mechanisms by which growth-environment factors affect fiber quality are incompletely documented. Mapping fiber quality variations according to fruiting site shows that the fiber properties most closely related to maturity depend on source-boll position on the plant and, thus, on flowering date and the environmental conditions prevailing during maturation of that source-boll. Fiber maturation rates are particularly sensitive to temperature, and strong correlations exist between heat-unit accumulation and maturity-related fiber properties, i.e., circularity, immature fiber fraction, cross-section, and micronaire. Depending on the boll location on a plant and the location of that plant in the field, each boll develops and matures in a slightly different growth micro-environment. These variations in growth environment amplify the natural variability in cotton fiber properties, particularly fiber 'fineness' and maturity. Environment-related variability in fiber cross-sectional shape and maturity persists through fiber processing as problematical variations in yarn evenness, strength, and dye-uptake. These variations in the processed fiber are as directly linked to growth environment as are the accepted relationships between weather and fiber yields. Thus, in the design of environment-responsive management systems for cotton production, it is essential that higher yields not be accompanied by increased variability in fiber properties, variability that significantly lowers fiber utility values.