An overview is presented of computer modeling and simulation methods that play an increasing role in drug design: quantum chemical methods, molecular mechanics, molecular dynamics and Brownian dynamics. The application of molecular dynamics for the prediction of thermodynamic properties like free energy differences and binding constants is discussed. The Brownian dynamics method is presented in connection with the calculation of effective electrostatic forces using the Poisson-Boltzmann equation, which allows one to sample ligand-binding geometries and to predict the kinetics of diffusion-limited enzyme reactions. New techniques that have recently been extensively developed, such as the global energy minimization and quantum-classical dynamics methods, are also introduced. The molecular modeling methods are illustrated with selected examples.