The Anisotropic Virial-Biased Sampling for Monte Carlo Simulations in the Isobaric-Isothermal Ensemble Abstract: The original virial-biased sampling of Mezei [1] that changes the simulation cell's volume isotropically has been generalized to anisotropical changes. Calculations on liquid water and the aqueous solution of the dimethyl phospate - sodium ion pair demonstrate the computational gains of the virial biased techniqes.