Conversion of hot coke oven gas (COG, containing tarry material) into light fuel gas over a Ni/Al2O3 catalyst was studied. Laboratory scale tests were carried out in a two-stage fixed-bed reactor at ambient pressure. The nickel catalyst promoted the hydropyrolysis reaction of tarry materials. High yields of total product gas and methane were obtained at high hydrogen concentrations. If the hydrogen supply was adequate for hydropyrolysis of the tarry material, conversion of coal volatiles was high, at more than 95% on carbon balance, even with a gas residence time as short as 0.15 s in the catalyst bed. The product gas yield depended on catalytic temperature. At 923 K, the maximum conversion of coal volatiles into the light gas was achieved at 95.0% on carbon balance, with methane 86.7 vol% of the carbonaceous gas product. Although carbon deposits deactivated the catalyst after a long period of use, the catalyst could be regenerated by treatment with oxygen at 800 K, providing high activity in subsequent decomposition of tarry material. The influence of sulphide on the tarry material decomposition reaction was small even in a 2000 ppm H2S atmosphere.