Effects of dissolved oxygen and/or dissolved hydrogen on stress corrosion cracking growth rates of 304L(N), 316L(N) stainless steels and weld metals in high temperature water environments were investigated by using fracture mechanics specimens and alternating current potential drop technique.The results are compare with those for sensitized stainless steels.Four types of dependence of crack growth rates on electrochemical conditions were observed in the experimental data for non-cold worked, cold worked, sensitized stainless steels and weld metal.Crack growth rate in austenitic stainless steels increased with increasing dissolved oxygen or electrochemical potential, and the effect of electrochemical potential was more significant in non-hardened stainless steels than in their hardened counterparts.A peak in CGR vs.dissolved oxygen was observed for in a 316NG weld metal with a relatively high content of ferrite, which was not observed in a 316NG weld metal with a relatively low content of ferrite.These results show the strong interaction between crack tip mechanics and crack tip oxidation kinetics.