Yield model was developed for selected cotton genotypes (Gossypim barbadense. L). Yield was equated with the volume of rectangular parallelepiped having the following dimensions, bolls per square meter (X), seed per boll (Y) and seed cotton per seed (Z). Axis (Z) was divided into its two fractions, lint per seed (L/S) and weight per seed (SW/S). Meanwhile, lint yield was expressed by rectangular parallelepiped (XYL).Yield components of the selected genotypes were expressed as a percentage of Giza90 over five locations in Middle and Upper Egypt in 2007 season. The results showed that, bolls per square meter (X axis) had the greatest influence on yield. Breeder expects that the greatest gain in yield improvement should come from exerting selection pressure on this character. Concurrent selection pressure should also be placed on seeds per boll (Y) and seed cotton per seed (Z). Data were presented to illustrate a use of model to define the component of yield more susceptible to alteration to increase yield.