An AISI 420 (13Cr) martensitic stainless steel was tested in environments containing different amounts of H 2S, CO 2, Cl − and acidity, at temperatures varying from 22 to 140°C. The sulphide stress corrosion cracking (SSCC) resistance was assessed with three different types of testing methods: uniaxially constant load; constant strain (U-bend) and slow strain rate (SSRT). High susceptibility to SSCC was evidenced in H 2S environments, while CO 2 additions had an inhibitive effect due to the formation of protective films. High Cl − concentrations and low pH had a detrimental effect. Moreover, SSCC susceptibility was related to the actual corrosion rate: high corrosion rates caused more delocalized attack. In this regard, chlorides, H 2S and acidified pH may increase the corrosion rate with a final beneficial effect on SSCC behaviour. The SSRT technique, due to its high sensitivity, showed stress corrosion cracking also in H 2S-free solutions saturated with CO 2, whereas U-bend specimens remained intact. The application of 13Cr stainless steel can be proposed for use in environments with high pCO 2 and low pH 2S. The maximum allowable pH 2S is a function of temperature, pH and Cl −.