This paper describes the results of a laboratory study evaluating stress corrosion cracking resistance of alloy CA6NM (UNS J91540) in highly sour environments and the implications of the findings on the usage of CA6NM in wellhead components. CA6NM is a commonly used material in wellhead tree components and valve and choke components in oil and gas production. NACE MR0175/ISO15156-3 permits the use of CA6NM in the proper metallurgical condition for these applications in any oil and gas production environment providing the pH of that environment is greater than or equal to 3.5. In order to verify the performance of CA6NM in reasonable worst case oil and gas production environments an experimental program was conducted to assess the stress corrosion cracking resistance of three heats of CA6NM in multiple modified NACE Level VII environments. NACE Level VII is defined in NACE MR0175/ISO15156-3 as consisting of 151700 mg/kg Cl- 500 psia H2S and 500 psia CO2 at 401 F. The experiments conducted in this study evaluated three heats of CA6NM for stress corrosion cracking resistance in NACE Level VII modified by addition of bicarbonate to achieve pH 3.5 at various temperatures and applied stress levels.