Steam reforming of methane, kerosene and heavy oil over a nickel/alumina commercial catalyst and other materials such as limestone, dolomite and iron ore, was studied using a 5 cm i.d. fluidized bed reactor. The effects of operating parameters on conversion, hydrogen yield, product gas composition and elutriation of fine catalysts were investigated. It was found that a fluidized bed is flexible enough to handle various feedstocks, including hydrocarbons heavier than naphtha, because it permits the addition of catalyst to, or withdrawals of, coked catalyst from the bed. The yield of hydrogen obtained from fluidized bed steam reforming of heavy oil at 800℃ over limestone was similar to that obtained over commercial nickel-based catalyst. This indicates that limestone could be a promising catalyst for the rpoduction of hydrogen from heavy oil. However, hydrogen yield decreased with reaction time in the experiments using the limestone catalyst. The main cause of the decrease in hydrogen yield was elutriation of fine catalysts from the bed during the reaction.