Austenitic stainless steels and Ni-based alloys are major construction materials for pressurized water reactors (PWRs). To mitigate the risk of material degradation and to control the fission rate in the reactor, water chemistry modifications are made to PWR primary water including dissolved hydrogen (DH) additions and the pH control using Li additions. The aim of this study is to investigate the influence of low dissolved hydrogen (5 cc/kg H2O) and B/Li concentration on the primary water stress corrosion cracking (PWSCC) response of Alloy 600 and SS 316L at 320°C in a simulated PWR primary water environment. The SCC behaviors were investigated via slow strain rate tensile (SSRT) tests. The morphologies and microstructure of the samples were observed by scanning electron microscopy (SEM) and laser Raman spectrophotometer analyses. The Alloy 600 thermally treated (TT) sample tested at 1200 ppm B + 3.5 ppm Li with a DH of 5 cc/kg H2O showed the worst degradation in the mechanical behavior due to SCC among the Alloy 600 samples. The 316L sensitized (SEN) sample tested in an environment with 300 ppm B + 1 ppm Li and a DH concentration of 5 cc/kg H2O showed the lowest ultimate tensile strength (UTS) among the 316L SEN samples tested. In addition, the mechanical performance of the Alloy 600 samples was better than that of 316L samples.