This study is concerned with the effect of chemical, electrochemical and mechanical surface preparation on initiation of strees corrosion cracking of austenitic and ferritic stainless steels in 300°C water containing 600ppm of chloride ion. Steels dealt with this report consist of commercial type 304, 316 and 430 stainless steels and laboratory melted 18 Cr-5 Ni and high purity 18 Cr-8 Ni steels. The results obtained can be summerized as follows: (1) The methods for preparing surfaces of specimens of annealed type 304, type 316, 18 Cr-5 Ni and high purity 18 Cr-8 Ni alloys and senditized type 304 steel exposed to high temperature water can produce a significant effect on susceptibility to stress corrosion cracking. Chemically or electrochemically polished specimens exhibit greater resistance to cracking than mechanically polished specimens. (2) Specimens of annealed and sensitized type 430 stainless steel, however, were not affected by the method for preparing surface. (3) Surface roughness of mechanically polished specimens appears not to be responsible for the shorter life to cracking of these specimens. (4) Oxide films grown in high temperature water on chemically or electrochemically polished specimens were dense and adherent in contrast with the porous and non-adherent oxide on mechanically polished specimens. Specimens with the former type oxide were less susceptible to cracking than specimens with the latter type oxide. (5) The protective nature of chemically or electrochemically polished specimens disappeared through cathodic treatment in 2 N-H₂SO₄ solution. (6) The effects of various surface preparations appear to opearate through the influence of their surface film formed during polishing. (7) Soft X-ray analysis of surface layer revealed the enrichment of nickel and chromium on the chemically or electrochemically polidhed specimens. This layer also, at least partly, contribute to inhibitive action to cracking of chemically or electrochemically polished surface.