Doctoral candidate Greg Howard recently presented a talk titled "Modeling Mixtures of Full and Partial Agonists Using Generalized Concentration Addition" during the Computational Approaches session of the 2007 SBRP annual meeting in North Carolina. Greg's work, with Tom Webster (project 2), focuses on methods for assessing and predicting interactions-additive, synergistic, or antagonistic- between toxic exposures. Recently, this has included developing a model of additivity for mixtures of full and partial-agonist dioxin-like agents, as well as rationalizing definitions of additivity in toxicology and in epidemiology.