The effects of prior cold work (CW) and sensitization treatment on the stress corrosion cracking (SCC) behaviour of Type 304 stainless steels have been studied in chloride solutions using electrochemical tests and magnesium chloride tests with U-bend specimen. The results indicated that the SCC behaviour of the CW steel was essentially different from that of the solution-annealed steel. Intergranular stress corrosion cracking (IGSCC) of solution-annealed material changed into a mixed mode or dominant transgranular stress corrosion cracking (TGSCC) when the degree of CW was increased. The sensitization treatment enhanced IGSCC susceptibility by shortening failure time and accelerating crack initiation and propagation rates, but this effect was different for several other degrees of CW. These effects were revised taking into consideration the electrochemical and microstructural phenomena. The most dangerous degrees of deformation for different sensitization conditions for the development of IGSCC and TGSCC processes have been determined.