The study of insect-pest management systems requires knowledge of the effectiveness of applied insecticides. The study reported here was conducted to develop a method to estimate insecticide induced mortality of an insect population depending on the rate of application, the persistence of the insecticide, a dosage-mortality relationship, and the time of exposure of the insects to a treated area. A logarithmic equation was developed to estimate the cumulative percent mortality with time. The model was validated using mortality data for boll weevils,Anthonomus grandisBoheman, exposed to 2 rates each of azinphosmethyl and methyl parathion. The method developed in this paper can be used to study insect population dynamics as affected by the timing and rates of insecticide applications, increasing insect resistance to insecticides, and the use of different insecticides.