Steam reforming of oils derived from plastics has been investigated to produce gas from waste plastics. Two types of oils, from polyethylene and from polystyrene, were produced by thermal decomposition at relatively low temperatures (350-450 degrees C). Steam reforming of these oils was conducted at temperatures from 650 to 850 degrees C under a pressure of 1 atm using three types of Ni-Al2O3 catalysts. Gas yield, gas composition, carbon conversion, and the coking ratio for these catalysts were measured. Although the plastic-derived oils contain heavy hydrocarbons or aromatics, they are gasified well with a low coking rate at temperatures above 800 degrees C and a steam carbon ratio = 3.5 and LHSV = 1 h(-t). Among the three catalysts, C11NK, which is a commercial steam reforming catalyst for naphtha, possessed moderate activity, but had the lowest rate of coking. Gas compositions agreed well with values calculated from chemical equilibria. Product gas contained approximately 72 vol% hydrogen for polyethylene-derived oil and 68 vol% for polystyrene-derived oil.