Round-robin tests were conducted in order to investigate a canister method for determining standard gas mixtures of volatile organic hazardous air pollutants by 14 members of the Association for Environmental Analysis in Osaka. A first standard gas containing seven analytes (acrylonitrile, dichloromethane, chloroform, 1, 2-dichloroethane, benzene, trichloroethylene, and tetrachloroethylene at ca. 300 ppm each) was prepared in a glass vessel from their mixed solution according to our previous paper. An aliquot of this gas was transferred into a canister (61) using a syringe, and diluted (ca. 10 ppb each). The resulting standard gas mixture was evaluated by GC/MS after concentration. The obtained results prove this method to be both accurate and precise for the preparation of a standard gas mixture at low ppb levels. Another gas mixture containing nine analytes (vinyl chloride and 1, 3-butadiene in addition to the above-mentioned seven compounds at 3 ppb each) was also prepared in a canister, and similarly treated by GC/MS. It was found that the canister method is remarkably accurate and precise. However, the acrylonitrile values had in large standard deviations.