A method to determine the flash-and self-ignition temperatures of dried sewage sludge is described.A hot air furnace, similar to that used in ASTM Standard D 1929, was used to test two municipal and two industrial sludges. The flash-ignition temperatures ranged from 344 to 432°C, and the self-ignition temperatures ranged from 439 to 481°C. These ignition temperatures may be useful in assessing the potential of sludge combustion in dryers or in storage.