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. A
s a potential energy surface interpretation of thermodynamics and kine
tics 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 s
imulations can aid in the interpretation of experimental data for the
solvation of myoglobin is presented. It is argued that the advent of b
etter theories and increasingly faster computers will provide the oppo
rtunity for the application of more rigorous solvent models for the st
udy of complex biomolecular solutions with increasingly more accurate
results.