Currently applied models for the treatment of solvent in biomolecular systems are reviewed. Solvent models ranging from purely continuum to quantum mechanical in nature are discussed, together with their ranges of validity and the approximations inherent to the various methods. As a potential energy surface interpretation of thermodynamics and kinetics is a useful and familiar tool to the physical chemist; we use the generalization to free energy surfaces (or potentials of mean force) to unify the discussion where possible. An example of how theory and simulations can aid in the interpretation of experimental data for the solvation of myoglobin is presented. It is argued that the advent of better theories and increasingly faster computers will provide the opportunity for the application of more rigorous solvent models for the study of complex biomolecular solutions with increasingly more accurate results.