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. In ECBC-TR-224 and ECBC-TR-337, individual susceptibilities for both the general population and the military subpopulation were modeled by a lognormal distribution. The assumption of a lognormal distribution of individual susceptibilities for both the general population and a subpopulation cannot be correct. This report presents an alternative model and compares the previous and new models.