A bstract: - Predictions of the response of civil engineering structures cannot be correctly performed if the behaviors of concrete, steel and of the steel concrete interface are not well captured. In this paper, we are interested in the response of the interface between concrete and steel fibers or bars. Several results from pull out tests are presented. This study is aimed at obtaining reliable data on the effect of the state of stress in concrete on the response of the interface. It is found that the confinement stress has no effect on the fiber-concrete interface and that is has a significant influence on the response of the interface between reinforcing bars and concrete. These results will eventually help at identifying debonding and friction laws.