The analytical ability of participating laboratories were evaluated in the Proficiency Analytical Testing (PAT) Program to provide assistance in improving their performance. The sets of samples in the PAT Program included metals, silica (14808607), asbestos (1332214) fiber counting, and organic solvents. The reported results of the laboratories for the samples were compared against an acceptable performance limit. In PAT Round 117, conducted in April of 1994, results for the study were submitted from 1,304 participating laboratories. Of those laboratories, 91.3% were rated as overall proficient. The reference values, performance limits, and participants of each sample type were presented. There were 1,366 laboratories rated based on their performance from PAT rounds 114 to 117, July 1993 to June 1994. In determining metals, 91.4% were proficient; for silica, 98.9% were proficient. For asbestos determinations, 94.3% were proficient and for determining organic solvents, 87.6% were proficient. Plans for the future of the program include increased testing for organic solvents.