The results of Round 130 of the Proficiency Analytical Testing (PAT) Program, conducted in July 1997, were presented. The PAT Program is an effort to evaluate the analytical ability of occupational health laboratories by providing each affiliated laboratory with quality control reference samples for analysis on a quarterly basis. Laboratories are evaluated by comparing their reported results against an acceptable performance limit. Of the 1,240 laboratories enrolled in the PAT Program, 1,122 submitted results for Round 130. The analytical findings of the participating laboratories were compared to those of the reference laboratories, selected for their high PAT proficiency and American Industrial Hygiene Association (AIHA) accreditation. Round 130 was the first PAT round which included samples contaminated with n-butyl-acetate, ethyl-acetate, and isopropanol. Other contaminants analyzed included cadmium, chromium, lead, silica, and amosite fibers. The relative standard deviations were especially high for isopropanol. This was attributed to the absence of a coeluting solvent in analysis. For Round 130 of the PAT Passive Monitor program, which also took place in July 1997, 173 kits composed of two passive monitors exposed to benzene, toluene, and o-xylene were sent to participating laboratories. A total of 157 laboratories submitted 170 reports. The acceptable performance limit for AIHA accreditation was the reference value +/-18%. PAT Round 131 was sent to participating laboratories in October 1997. Results for analyses of methanol, cadmium, lead, zinc, silica, and chrysotile fibers were forthcoming. The authors conclude that the primary goal of the PAT Program, a collaborative effort of the AIHA and NIOSH, is to help occupational health and environmental laboratories worldwide improve their laboratory performance. Laboratory performance is determined by performance in the PAT Program over a 1 year period.