Metal dusting has been responsible for a number of material failures in the chemical processing, thermal treatment and ore-reduction industries. Increasing severity of metal dusting attack has been associated with increasing ratios of carbon monoxide-to-carbon dioxide and decreasing ratios of steam-to-hydrogen, which act to simultaneously increase carbon activity and decrease oxygen partial pressure. Testing has been performed to examine the effects of alloying elements and surface condition upon the metal dusting resistance of numerous alloy systems in a hydrogen-carbon monoxide gas mixture at 621°C. Measurements of mass-loss rate, pit-progression rate, and pit distribution have been utilized to rate alloy performance. Keywords: carburization, ferritic steels, iron-nickel-chromium alloys, metal dusting, nickel-base alloys, stainless steels