Stainless steels play an essential role in all sectors of the oil and gas industry, both upstream and downstream. In the past, this has predominantly entailed established grades, but the last 10 to 20 years have seen major changes in the design and use of stainless steels for oil and gas service. A range of low carbon 13%Cr martensitic, highly alloyed austenitic and two phase ferritic-austenitic steels has been developed offering improved properties and cost effectiveness for a wide range of duties, and the materials are being employed in increasing tonnages. However, the practical application of such steels is critically dependent on the use of welding for fabrication, since a welding operation can have a significant influence on the corrosion performance of the completed assembly. The paper considers the welding behaviour of the new steel types relative to older grades. Potential problem areas are identified, with the aim of indicating the controls necessary so that full advantage can be taken of the attractive base metal properties.