This document is Volume 3 of a series of reports entitled ''Geological Evolution and Analysis of Confirmed or Suspected Gas Hydrate Localities.''Volume 3 is an analysis of the ''Formation and Stability of Gas Hydrates in the Western Gulf of Mexico.''This report presents a geological description of the western Gulf of Mexico, including regional and local structural settings, geomorphology, geological history, stratigraphy, and physical properties. It provides the necessary regional and geological background for more in-depth research of the area. Detailed discussion of bottom simulating acoustic reflectors, sediment acoustic properties, and distribution of hydrates within sediments is also included. The formation and stabilization of gas hydrates in sediments are considered in terms of phase relations, nucleation, and crystallization constraints, gas solubility, pore fluid chemistry, inorganic diagenesis, and sediment organic content. Together with a depositional analysis of the area, this report is a better understanding of the thermal evolution of the locality. It should lead to an assessment of the potential for thermogenic hydrocarbon generation. 271 refs., 75 figs., 7 tabs.