This critical compilation of virial coefficients of pure gases was prepared from the virial coefficient database at the Thermodynamics Research Center, formerly at Texas A&M University, College Station, Texas and now located at the National Institute of Standards and Technology, Boulder, Colorado. The virial coefficient data in this compilation will be of interest to the theoretical chemist as it includes the many sets of accurate gas imperfection data which have been determined over the past twenty years by improved methods of gas density determination, by isochoric Burnett coupling methods and from speed of sound measurements, as well as by the more traditional techniques. The needs of the industrial chemist are met by these more reliable data and also the increased number of compounds for which data are now available.