Erickson, R. J., Bills, T. D., Clark, J. R., Hansen, D.J., and Knezovich, J., 1994, Synopsis of discussion session on physicochemical factors affecting toxicity, Hamelink, J. L., Landrum, P. F., Bergman H. L., and Benson, W. H., eds., Bioavailability physical, chemical and biological interactions: Boca Raton, Lewis Publishers, p. 31-38. Abstract The paper documents the workshop discussion regarding the role of these factors in altering toxicity. For each factor, the nature, magnitude, and uncertainty of its empirical relation to the toxicity of various chemicals or chemical classes is discussed. Limitations in the empirical database regarding the variety of species and endpoints tested were addressed. Possible mechanisms underlying the empirical relations are identified. Finally, research needed to better understand these effects is identified. Keywords *Toxicity, *Physicochemical Properties, *Aquatic Biology, Chemical Compounds, Bioaccumulation, Metals, Temperature, Ph, Salinity, Aquatic Ecosystems, Data Bases, Toxic Substances, Reprints, Ntisepaord