Modified 13Cr martensitic stainless steels and 22Cr duplex stainless steels are both of interest in slightly sour oil and gas producing environments. The cost differential between these materials is now less than that which exists between standard 13Cr and 22Cr categories. Whilst these standard 13Cr grades are presently the workhorse material for downhole tubulars in the North Sea, as higher temperature (HPHT) wells are being developed, the need for more corrosion resistance will mean increased use of 22Cr duplex or modified 13Cr. The performance of these materials will be compared, particularly in terms of corrosion at elevated temperature (150–200°C) and sulphide stress cracking at low temperature (typical shut-in conditions). Each alloy type has its generic strengths and weaknesses; these dictate the conditions in which each can be used.