Soil vapor extraction (SVE) and bioventing (BV) are proven strategies for remediation of unsaturated zone soils. Mathematical models are powerful tools that can be used to integrate and quantify the interaction of physical, chemical, and biological processes occurring in field scale SVE/VB systems. This report describes the conceptual and mathematical formulation, numerical implementation, and application of a multiphase, multicomponent, biodegradation model designed to simulate physical, chemical, and biological interactions occurring in field scale SVE and BV systems. The model, the Michigan Soil Vapor Extraction Remediation Model (MISER), is two-dimensional and may be run in a cross-sectional or axisymmetric mode. Phase and constituent mass balance equations are discretized with a standard Galerkin finite element approach using linear triangular elements. A modular, set-iterative solution algorithm is employed. Features of the model include: the ability to simulate multiphase gas and aqueous fluid flow; the simulation of multicomponent transport processes, incorporation of rate-limited interphase mass transfer for volatilization and dissolution of an entrapped organic liquid, volatilization and sorption of aqueous phase constituents, and biophase update; and the simulation of multicomponent biodegradation kinetics and microbial population dynamics. A complete description of the computer code, implementation procedures, and example SVE and BV simulations is included.