The vibration criterion (VC) curves, commonly used in the design of facilities which house vibration-sensitive instruments and tools, were developed by the author and his colleagues, in the early 80's, published by SPIE in 1991 and by IEST in 1993. Each of the criterion curves A through E is associated with a 'line width' or 'detail size' which was an attempt by the authors to describe the capabilities of the tools with which each curve might be associated. In the years since the curves were developed there have been substantial developments in tool design and isolation. In this paper the curves are reviewed in the context of present-day tools and processes. Changes are proposed where these might be justified.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.