Cotton (Gossypium spp.) lint yield is reduced by pink bollworm, Pectinophora gossypiella (Saunders), infestations. The cut-boll technique of estimating pink bollworm infestations underestimates by a factor of 3 the number of larvae in the bolls as compared to the incubated boll technique. The boll susceptibility to pink bollworm infestation is highest during the third to fifth week after flowering. The numbers of pink bollworms per boll may increase during these weeks. Early season infestations appear to increase boll rot. All of these relationships are built into an experimental model to estimate the potential lint yield reduction from weekly counts of flowers and pink bollworm larvae in bolls.