Numerous runs of GOSSYM, the cotton growth simulation model, were made to determine the effects of individual parameters in the GOSSYM calibration files. Results of these runs were used in a series of sensitivity analyses to determine the magnitude of these effects and to classify the sensitivity of each factor under different conditions. Calibration factors were traced throughout the program operation, and their functions were defined. This information is being used to apply variety-specific plant characteristics to the development of calibration files for High Plains cotton varieties.