To clarify the relationship between the compound layer formed on the nitrided specimens and the friction and wear properties, pure iron and Fe-1Cr alloy were nitrided at various conditions then their friction and wear behaviors under lubricated condition were investigated. The compound layer structures consisting of γ’ single phase, ε/γ’ mixture containing voids and ε/γ’ mixture containing lesser voids were prepared. The wear rate decreases monotonically as the increase of surface hardness, which mainly depends on the fraction of voids. On the other hand, the friction coefficient decreases with an increase of the fraction of void up to 6％, whereas the friction coefficient increases at the fraction of void above 6％. This is because that the oil storage effects in voids can reduce the friction coefficient at low void fraction meanwhile the easier peeling of the compound layer occurs at high void fraction leading to the increase in friction coefficient. Those results well support the advantage and disadvantage of voids on friction coefficient reported so far.