CO2-SCC of seven quenched and tempered, high strength low alloy steels has been demonstrated in a series of laboratory experiments that were designed to study the effect of temperature, specimen loading (dynamic and static), strain rate, oxygen variation via deaeration technique, test temperature, and yield strength. The mode of fracture was exclusively intergranular. In this study, stress corrosion cracking experiments were performed in aqueous solutions with and without NaCl, and 0 to 1000 psi (6900 kPa) CO2, while at temperatures from 150 ° to 400°F (66 ° to 204°C). For these quenched and tempered, high strength, low alloy steels, the susceptibility to CO2- SCC increased with dissolved oxygen, CO2 partial pressure, and yield stress. The effect of NaCl varied. Maximum susceptibility occurred between 150 ° and 350°F (66 ° and 177°C). Dynamic straining at low rates, i.e., 2 x 10 -6 sec-1 and less, demonstrated a wider range of materials and temperatures for which CO2-SCC can occur. Although no field failures are known to have occurred downhole by this mechanism, these results cause concem regarding the use of these steels in production environments with high concentrations of CO2. More work is required to fully define the environmental and material envelopes of use of high strength steels in sweet high temperature, high pressure wells