The influences of carbon on microstructures and properties of wrought steels are discussed. The basic metallurgical knowledge has showed fora long time that the optimum properties depending on alloy additions can be achieved only by a correct control of carbon content. From the comparison between porous and fully dense steels it comes out that carbon control is always a critical factor for achieving the highest properties. The thermodynamic bonds concerning carbon equilibria during sintering are discussed and the possible interactions with various controlled atmospheres are examined. Some atmospheres can cause carbon depletion or enrichment, whereas other gas compositions do not modify the equilibria. In case of chemical changes during sintering, involving carbon, the temperature profile may be a critical item. The microstructures after cooling obviously depend on thermal gradients within certain temperature ranges. The requirements to be Fulfilled on furnaces, to control sintered properties, are discussed. Some common schemes of equipment are analysed and their suitability to a correct carbon and microstructure control during sintering is surveyed. Sintered samples produced at different plants under industrial conditions and having various chemical compositions have been observed under the optical microscope and at the SEM. The observations show that microstructures can span from ferrite-pearlite mixes to austenite-bainite ones, even when copper is the only alloy addition besides carbon. Diffusion-bonded powders containing also nickel and molybdenum allow to get hard phases even at relatively low cooling speeds, The strength levels are suitable to fulfil exacting demands and can promote new advanced applications of P/M parts.