The pyrolysis of waste sludges was investigated using thermogravimetry/mass spectrometry (TG/MS) and a fixed-bed reactor. Two types of sludge were used, namely mixed sludge and oil sludge. In TGA/MS measurements, two degradation steps were observed. Degradation of organic structures, in sludge took place in the first step, while inorganic materials in sludge were mainly decomposed in a second step (above 500 degrees C). In a fixed-bed reactor, the catalytic effect of inorganic matter in addition to organic matter was monitored the quality and yield of products from pyrolysis. Pyrolysis of oil sludge produced a larger amount of oil containing more aliphatic compounds and a high calorific value. On the other hand, pyrolysis of mixed sludge gave a smaller amount of oil being rich in polar compounds. The gaseous products from pyrolysis consist of high amount of combustable gases. Landfilling was found to be the best alternative to dispose off the pyrolytic char obtained from pyrolysis. (C) 2005 Elsevier Ltd. All rights reserved.