Carburizing is one of the leading surface-hardening processes applied to the sintered@ low-alloyed steel parts in the automotive industry. While diffusion of carbon in wrought steel is well documented@ this is not the case for PM steel subject to carburizing in vacuum furnaces. In this paper we present results that show that the density of the powder metal is the main factor for the final carbon content and distribution. Also important is the state of the surface of the part; either sintered with open porosity or machined with closed porosity. The way the carburizing gas moves through the furnace might be of some influence as well.