Interest in very low carbon (0.02%) steel containing 0.10 percent niobium emerged as early as 1962 [1] at the inception of the authors PhD studies.Full scale demonstration heats were produced by Bofors Steel Plant in 1972 and were converted from slabs to plates by nine different steel mills [2].This chemical composition permits the production of high strength high toughness plate (and thus pipe) using relatively high finish rolling temperatures (as high as 950°C),the so called High Temperature Processing Concept (HTP).Commercial application first occurred in Canada in 1974 [3] but it was used only sporadically after that,until 1998 when it was applied for the X-70 Sour Service Cantarell Project in Mexico [4].Soon thereafter,the El Paso Cheyenne Plains Project used a 0.05%C 0.095%Nb 0.27%Cr variant of the HTP steel [5] for their Wyoming to Kansas 618 km pipeline.Nowadays the HTP concept is being utilized for construction of approximately 6000 km of 48" OD x 18.4 mm X-80 per year in China and for smaller projects elsewhere.A summary of the metallurgical principles and history of the development are presented in detail in the paper.