A Heliotois spp. damage submodel, HELDMG, was developed to allow a Heliothis model to be linked with the cotton model GOSSYM. HELDMG predicts the within plant distribution of Heliothis damage in cotton. During the 1988 growing season, I compared HELDMG's predictions to observed distribution of damage within the cotton plant. The submodel accurately predicted the vertical and horizontal distribution of square damage. However, HELDMG predicted more boll damage in the middle 1/3 of the main stem and on the vegetative stems than actually occurred. This was caused by the fruit predation submodel used in HELDMG assigning too much of the damage to flowers and small bolls. If HELDMG assumed that the proportion of damage occurring on flowers, small, medium, and large bolls was proportional to number present, then the prediction improved. Accurately predicting the distribution of Heliothis damage within the cotton plant will improve our precision in estimating the effect of Heliothis damage on cotton growth and yield.