[en] The results of a radiological survey of the former Vitro Rare Metals Plant in Canonsburg, Pennsylvania, are presented in this report. This 18-acre site was used from 1911 to 1922 to extract radium from carnotite ore, from 1930 to 1942 to extract radium and uranium salts from onsite residues and carnotite ore, and from 1942 to 1957 to recover uranium from various ores and scrap materials. The radiological survey was conducted in two phases. Phase I included measurement of radon and radon daughter concentrations in onsite buildings; concentrations measured in this part of the survey were well above guideline levels. Phase II consisted of measurement of surface contamination levels on the site, external gamma radiation levels at 1 m above surfaces on and near the site, radionuclide concentrations in surface and subsurface soil and water on and near the site, and radon concentrations in air at offsite locations. The results of the second phase of the survey indicate that large quantities of the radioactive wastes generated during radium and uranium recovery operations still remain on the site. Radium-bearing wastes are present in soil beneath or adjacent to each of the buildings on the site and in the top few feet of soil over almost the entire site, with some areas being contaminatd to a depth of 16 ft or more. Alpha contamination levels, beta-gamma dose rates, and external gamma radiation levels in some areas of the buildings and outdoors on the site are above current federal guidelines concerning the release of property for unrestricted use. Concentrations of ²²⁶Ra in water in holes drilled on the site are above the maximum permissible concentration. Also, measurements made offsite show that contamination from the site has spread to nearby offsite locations, and that there is significant atmospheric transport of ²²²Rn from the site