"Lattice-gas Monte Carlo Simulations in Electrochemical Surface Science" Per Arne Rikvold Department of Physics Florida State University Tallahassee, FL 32306 USA I will present a short introduction to the use of equilibrium and dynamic Monte Carlo simulations of lattice-gas models in surface electrochemistry. This introduction will be illustrated by examples of recent research by my collaborators and myself. The applications include: Adsorption of halides on single-crystal silver electordes; The effects of lateral adsorbate diffusion in a simple model of underpotential deposition (a nucleation-and-growth phenomenon); A new method to understand the dynamic details of electrochemical adsorption phenomena; And finally some simulations that suggest the possibility of a dynamic phase transition in the catalytic oxidation of carbon monoxide under oscillating-presure conditions.