The TINKER molecular modeling software is a complete and general package for molecular mechanics and dynamics, with some special features for biopolymers. TINKER has the ability to use any of several common parameter sets, such as Amber (ff94, ff96, ff98 and ff99), CHARMM (19 and 27), Allinger MM (MM2-1991 and MM3-2000), OPLS (OPLS-UA, OPLS-AA and OPLS-AA/L), Liam Dang's polarizable potentials, and our own AMOEBA polarizable atomic multipole force field. Parameter sets for other standard force fields such as GROMOS, UFF, ENCAD and MM4 are under consideration for future releases.