In this project in the Theoretical and Computational Chemistry Subprogram of the Physical Chemistry Program, Stell will study and develop theories using statistical mechanical models. The emphasis will be on results that can be obtained in analytic or quasi-analytic forms. Specific topics include (i) dielectric and optical theory, (ii) transport theory, (iii) percolation and gelation theory, (iv) development of predictive theories of n-particle distribution functions, (v) theories of charge and density profiles in pores and in fluids next to membrane and vesicle surfaces, (vi) microscopic models of microemulsions, (vii) models of associating particles.