Three differently prepared cobalt/ZSM-5 catalysts were investigated with respect to physical and chemical properties and to activity and selectivity for conversion of synthesis gas. The catalyst preparations consisted of the following: (1) direct decomposition of C/sub 5/H/sub 5/Co(CO)/sub 2/ on ZSM-5, (2) impregnation of ZSM-5 with an aqueous solution of cobalt nitrate, and (3) physical admixture of precipitated cobalt oxide with ZSM-5. At about 3 wt % cobalt loading, the first catalyst showed higher dispersion, higher (H/sub 2/ + CO) conversion, and about 10 times higher yield of gasoline-range hydrocarbons (g/h) than the catalyst prepared by the other two methods. Some H/sub 2/ and CO chemisorption studies and magnetization measurements were conducted to measure the average particle diameter. Infrared studies of chemisorbed pyridine of these samples indicate that ion exchange of Co/sup 2 +/ for acidic protons occurs in organometallic-impregnated and aqueous solution-impregnated catalysts. 18 references, 6 figures, 4 tables.