The U.S. Department of Energy, Federal Energy Technology Center, has sponsored a project to simulate the behavior of tight, fractured, strata-bound gas reservoirs that arise from irregular, discontinuous, or clustered networks of fractures. New FORTRAN codes have been developed to generate fracture networks, to simulate reservoir drainage/recharge, and to plot the fracture networks and reservoir pressures. Ancillary codes assist with raw data analysis. FRACGEN, the fracture network generator, implements four Boolean models of increasing complexity through a Monte Carlo process that samples fitted statistical distributions for various network attributes of each fracture set. Three models account for hierarchical relations among fracture sets, and two generate fracture swarming. Termination/intersection frequencies may be controlled implicitly or explicitly. Using an output file consisting of fracture end-point coordinates and apertures, NFFLOW, the flow simulator, then computes the transient flow rates or bottom-hole pressures according to user-specified pressure or rate schedules, respectively. The flow simulator divides each matrix block into subregions that drain to the midpoint of the adjacent fracture segments in accordance with a one-dimensional, unsteady-flow model. Each idealization approximates both the volume and the mean flow path of each subregion. There is no flow from matrix block to matrix block. Volumetric flow rate in the fractures is modeled as a linear (cubic law) function of the pressure difference between the recharge points and the fracture intersections. The linear function incorporates a "real gas pseudo potential," which allows viscosity and the z-factor to vary with pressure. A requirement of material balance among all intersections couples the individual recharge models together. The resulting equations for material balance at fracture intersections are solved by a Newton-Raphson technique that accommodates a slight nonlinearity caused by matrix recharge. A network consisting of 2300 fractures and 51 time steps was simulated in less than 1 hour (clock time) on a Pentium 200 equivalent computer.