guidelines present in various fabrication standards (mainly U.S. and UK) regarding the postweld heat treatment (PWHT) requirements of welds and the limits for as-welded construction made in pipes, pressure vessels, and structures, including bridges, buildings, and offshore structures, as discussed below. It is recognized that some codes now include provision for repair without PWHT (Refs. 1–3), and that there have also been investigations aimed at providing recommendations for acceptable thickness limits for the as-welded condition for general structural conditions (Refs. 4, 5). It is noted that steel making technology has changed over the last thirty years or so (although steels are also produced in parts of the world where steel making technology lags behind best practice). However, the fabrication codes were generally devised for older, normalized steels with higher carbon contents (Refs. 6, 7), and often with no toughness requirement. In addition, a number of methods available for gaining exemption from PWHT are examined, including specially designed weld repair procedures and a case-specific fracture mechanics approach (in Part 2). The general method adopted is that of Ref. 8, for which fracture mechanics testing, e.g., as in Ref. 9, is normally required. This investigation relates only to C-, C-Mn, and low-alloy steels. Some of the similarities and differences are considered, and testing required to move toward elimination of the apparent anomalies is considered. In compiling this article, the views of representatives of fabricators and end users have been sought. The objectives of the study were to identify the types of materials where industry considers that there are grounds for seeking wider exemption from PWHT; to compare and contrast the limiting thickness requirements above which PWHT is required and the associated Charpy test requirements for the as-welded condition in standards relevant to the fabrication industry; to investigate the methods available for gaining exemption from PWHT, namely the use of specially designed repair procedures and the specification of a minimum Charpy energy, calculated by a fracture mechanics approach; and to identify whether a future program of toughness testing and residual stress measurements on specific steels is needed to demonstrate a case for exemption from PWHT.