Stress Corrosion Cracking (SCC) behaviour of three austenitic (S31603, N08904, S20400) and three duplex (S31803, S32304, 21Cr1Ni4Mn.2N) stainless steels in 30% sodium hydroxide solution at 200°C was studied. The tests were conducted using the SSR technique at strain rates in the range 5x10^-6 to 4x10^-8 s^-1. The susceptibility to SCC increased monotonically by decreasing the strain rate and all the materials examined underwent SCC if the strain rate was low enough. On the whole the results pointed out that the duplex stainless steels S32304 and S31803 had better cracking resistance than austenitic stainless steels N08904 and S31603 and that the low nickel manganese-containing steels S20400, 21Cr1Ni4Mn.2N did not display any significant improvement in SCC resistance in comparison with the nickel-containing steels.