Brownian dynamics (BD) is a trajectory method developed to simulate the Brownian motion of whole macromolecules under the influence of complicated electrostatic and excluded volume interactions present in biophysical systems. The BD method is well suited to the study of biomolecule interactions such as protein-ligand and protein-protein interactions. BD is useful for identifying binding modes, is sensitive to protein mutations, and is valuable for following binding kinetics and thermodynamics. Applications to be discussed include glycolytic enzyme/F-actin and glycolytic enzyme/substrate interactions.