Most components are tempered after heat treatment operations such as case hardening or induction hardening. The common opinion is that the martensitic structure after heat treatment is too brittle and tempering is necessary to increase toughness. Tempering is an additional operation which leads to increased costs by energy, handling, and investments. Eliminating tempering from the heat treatment process leads to increased productivity, energy savings, and lowered environmental impact. Two carburised steels, Ovako 253A (~EN 22NiCrMo12-5F mod. A) and EN 20NiCrMo2 (SAE 8620, SS2506), were tested for contact fatigue resistance in a roller to roller rig. The tested samples were characterised with respect to amount of fatigue damage, residual stress, amount of retained austenite and hardness. The objective was to determine if tempering is always necessary after a heat treatment operation. The contact fatigue tests show that tempering results in lower contact fatigue resistance. Further, fatigue cracks were found to have initiated in different ways between tempered and untempered steel. Copyright © 2011 Inderscience Enterprises Ltd.