This paper examines the influence of oxygen traces on corrosion and hydrogen charging of steel in H2S containing environment. It is well known that H2S is the driving force for many types of steel failures such as hydrogen induced cracking (HIC), sulfide stress cracking (SSC), and stress-oriented hydrogen induced cracking (SOHIC). Since it is a huge concern for oil and gas industries, standard test methods have been developed and published as NACE technical methods (e.g. NACE TM0284 and NACE TM0177). Though it is recognized that oxygen pollution shall be avoided during H2S cracking tests, there is still a lack of experimental data to illustrate the potential impacts of a small oxygen pollution. The aim of the present study was to check if oxygen traces can modify corrosion mechanisms and hydrogen charging of steel in H2S medium. Experiments consisted in hydrogen permeation measurements through thin pure iron membrane. They were performed at corrosion potential in order to be in realistic environmental conditions. Corrosion rate was also evaluated through weight loss measurements. Analysis of test solutions was performed in order to identify reaction products between H2S and O2