Possibility to convert the tar vapor in the hot coke oven gas (COG) to a synthesis gas was investigated. Tar condensed from an actual COG as well as model compounds such as benzene, naphthalene, and pyrene were used as the reactants. Experiments of the pyrolysis and catalytic steam reforming of the tar in a helium, a steam, and a simulated COG atmospheres were carried out. More than 80% of tar could be decomposed in several seconds by pyrolysis at temperature greater than or equal to1000degreesC. The coke yield reached 80% and the main gas products were methane and hydrogen. Coke deposition was reduced in the presence of steam by steam gasification of the coke. When the tar was pyrolyzed in the simulated COG, coke deposition from methane in addition to the deposition from the tar was observed at high temperature. The reverse shift reaction forming carbon monoxide and steam also occurred during the tar pyrolysis in the simulated COG. The coke formation was not reduced greatly even in the presence of the reforming catalysts.