Civil defense planning requires estimates of the toxicity of chemical warfare agents to the general public, but the current toxicity estimates are for male soldiers. Individual susceptibilities for both the general population and the military subpopulation are modeled by a lognormal distribution. Historical military demographics are used to estimate the size of the subpopulation from which military personnel are drawn. Limits on the median effective dose and the probit slope of a subpopulation are determined as a function of the subpopulation size. The method of converting toxicity estimates is not limited to chemical warfare agents. Further, it may be used to convert toxicity estimates for the general population to toxicity estimates for a subpopulation; for example, the elderly. The modeling of subpopulations is not limited to toxicological applications. Blood lead data from the second National Health and Nutrition Examination Survey are compared to the subpopulation model.