The Process Piping Code—ASME B31.3, (“Chemical Plant and Petroleum Refinery Piping,” 1998 Edition, ASME, New York, NY) has undergone significant changes over the years to better serve the industries that it supports (Koves, W. J., and Frikken, D. R., 1996, “ASME B31.3: Recent Changes and Future Developments,” Pressure Vessel and Piping Conference, ASME PVP-Vol. 338). The Code has changed in response to changing technology, inquiries to the committee, technical needs, clarification of requirements and editorial considerations. This paper discusses the history of its development and provides and overview of the most significant changes to the Code. [S0094-9930(00)01303-2]