In this article, three commercial steels, JIS SCM 415, JIS SNCM 220 and AISI 1008 were carburized in a two-chamber vacuum furnace at temperature ranging between 900 and 1050 degreesC in an acetylene atmosphere. Steel SCM 415 consists of mainly 0.12% C, 1.0% Cr and 0.17% Mo, steel SNCM 220 consists of 0.18% C, 0.55% Mo, 0.42% Cr and 0.17% Mo, while steel AISI 1008 is a 0.058% C plain carbon steel. The carburized specimens were characterized for the hardness distribution and the microstructure of the carburized layers using thermodynamic analysis. Experimental results show that, under the same treatment conditions, the SNCM 220 steel exhibited the best performance in both the effective case depth (ECD) and total case depth (TCD) of the carburized layers. However, the carbon concentration in the carburized surface of the SCM 415 steel was higher than that for the SNCM 220 steel. The AISI 1008 steel was the worst among the steels investigated. Furthermore, the carbon potential of the atmosphere for the SCM 415 steel should be controlled lower than that for the SNCM 220 steel if the. same carbon concentration in the work surface is an essential requirement. The plain carbon steel AISI 1008 required the highest carbon potential among the three steels. (C) 2003 Elsevier B.V. All rights reserved.