The remarkable advances in quantum chemistry and molecular simulation that have occurred over the past decade make it possible to begin to simulate the kinetics of complex reaction systems. Herein, we describe the development of a first-principles-based Monte Carlo simulation for modeling catalytic surface kinetics. The simulation relies on a comprehensive kinetic database which is established from density functional quantum chemical calculations. The predicted elementary parameters include adsorption-, overall reaction-, lateral interaction-, and activation-energies. Bond order conservation and pairwise additive approaches are used to help complete the-lateral interaction effects. The Monte Carlo algorithm simulates an exhaustive ensemble of elementary steps, thus following the individual molecular transformations over a metal surface as a function of time and processing conditions. This molecular kinetic simulation was used to model the decomposition of NO on Rh(100) and the kinetics of ethylene hydrogenation on Pt. The results from these preliminary applications indicate that the molecular kinetic simulation can provide reliable temperature-program-desorption spectra and reaction rates that are within an order of magnitude of the measured values. By retaining the, explicit atomic structure, the simulation provides a detailed mapping of how the surface coverage, structure and composition control the surface chemistry and kinetics.