We investigate equilibrium properties and thermal etching of the {111} surfaces of silicon, both with and without perpendicular intersecting dislocations, using Monte Carlo computer simulation. A modified solid-on-solid (SOS) approach is employed which realizes the correct diamond-cubic (DC) crystal structure. Nearest-neighbor interactions are incorporated to model the bonding, while the effects of a dislocation are incorporated by the addition of an energy field modeled as a core region and an elastic strained region. Dislocations are seen to nucleate the etching process and result in the formation of etch pits. Etch rates and etch-pit morphologies are investigated as a function of the chemical potential driving force for etching, the temperature, and the energy parameters used to model the dislocation.