Hydrogen Induced Cracking (HIC) is a major issue of line pipe steels exposed to sour environments. In general 5.0 wt% NaCl and 0.5 wt% CH3COOH solution with 0.1 MPa H2S provided by NACE TM0284 as solution A is used to evaluate the HIC resistance of steel products. However in many cases the test condition is too severe compared to the actual field conditions. Therefore appropriate HIC evaluation method under sour conditions has been the subject of considerable investigations in recent years.High-strength Line Pipe (HLP) Committee of The Iron and Steel Institute of Japan (ISIJ) has proposed a HIC test solution with high buffering capacity for simulating and keeping aimed sour condition. The solution has high concentration of acetic acid and sodium acetate. In this study in addition effects of balance gas (N2 and CO2) on pH stability sour corrosion behavior and HIC susceptibility of carbon steel were investigated. From the results an appropriate test solution including balance gas is discussed from the viewpoints of convenience and effectiveness for evaluating the resistance of steels to HIC in sour conditions.