The background and current status of the Proficiency Analytical Testing (PAT) Program were discussed. The main goal of the PAT Program was regarded as the improvement of laboratory performance. The methods of the PAT Program were described, in which samples of metals, silica (14808607), fibers, and organic solvents, such as benzene (71432), chloroform (67663), and toluene (108883), were mailed to participating laboratories for analysis. The Pat Program was then able to inform these laboratories whether or not their analyses were accurate. As of July, 1996, 1,324 laboratories were enrolled in the PAT Program. Of these laboratories, 1,218 submitted results in round 126. The relative standard deviation (RSD) for the first cadmium (7440439) sample, adjusted to a lower concentration than usual, was 5.5%. The RSD for an asbestos (1332214) fiber sample, a synthetic fiber never tested previously, was 42.3%, the highest RSD determined in this round. The highest numbers of outliers were observed for the four asbestos fiber samples tested. Round 126 was also the first round in which passive monitors were evaluated. The future inclusion of additional organic solvents, such as methyl-ethyl-ketone (78933), methyl-isobutyl-ketone (108101), ethyl-acetate (141786), n-butyl-acetate (123864), and isopropanol (67630), was discussed. Round 127 of the Pat Program, which included chloroform, cadmium, silica, and chrysotile (12001295), was sent to laboratories in October of 1996. The results are forthcoming.