Molybdenum sulfide catalysts with surface areas ranging from 16 to 120 m(2)/g were prepared by the thermal decomposition of Mo(CO)(6) and H2S vapors in a specially designed tubular reactor system. The gas phase decomposition (GPD) reactions performed at 500-1100 degrees C produced only MoS2 when excess H2S was used. The optimum temperature range for the high-yield production of MoS2 was from 500 to 700 degrees C. By controlling the decomposition temperature, the Mo(CO)(6) partial pressure, or the inert gas flow rate, the surface area, oxidation state, chemical composition, and the grain size of the molybdenum sulfide product(s) were modified. At reactor temperatures between 300 and 400 degrees C, lower valent molybdenum sulfide materials, which were sulfur deficient relative to MoS2, were obtained with formal molybdenum oxidation states intermediate to those found for Chevrel phase compounds, M'Mo6S8 (M' = Fe, Ni, Co) and MoS2. By lowering the H2S flow rate used for the GPD reaction at 1000 degrees C, mixtures containing variable amounts of MoS2 and Mo2S3 were produced. Thus, through the modification of critical reactor parameters used for these GPD reactions, fundamental material properties were controlled.