Most chemical reactions are carried out in solution. The solvent surroundings affect such reactions in a variety of important ways. For example, the rates of reactions between ionized molecules are often limited by the rate at which the reactants diffuse through the solvent and come into contact. Also, specific solvation effects often determine the relative free energies or stabilities of reactant, transition state, and product molecules. In our group, we study such phenomena using methods from statistical mechanics. These methods range from simulation studies, in which the equations of motion of the atoms in a model system are solved on a computer, to formal studies in which we develop and solve differential or other equations.