Two simulation methods are presented for generating a grand canonical ensemble of molecules with internal degrees of freedom. Molecular dynamics integration is used as a Monte Carlo perturbation move in these methods. The integration move helps to explore the intramolecular degrees of freedom with high acceptance ratios. The proofs of the acceptance criteria for both methods are presented. Tests are described to show that the simulation produces results matching an analytical solution for a simple test system. The method is further tested by predicting adsorption isotherms of n-butane in the zeolite silicalite. An example using these algorithms to generate adsorption isotherms of more complex chiral molecules in chiral zeolitelike materials is also presented. (C) 2003 American Institute of Physics.