Preliminary results of round 115 of the Proficiency Analytical Testing (PAT) program were discussed. A total of 1,474 laboratories were enrolled in the PAT program, which was a cooperative program of the American Industrial Hygiene Association, Centers for Disease Control, and NIOSH directed at improving the analytical proficiency of the participating laboratories. Participating laboratories were sent a set of reference samples every calendar quarter (round). The ability of the laboratories to analyze these samples was evaluated and feedback was given before the next round. A total of 1,361 laboratories participated in round 115 in which they analyzed samples containing cadmium (7440439), lead (7439921), zinc (7440666), silica (14808607), chrysotile (12001295), carbon- tetrachloride (56235), 1,2-dichloroethane (107062), and trichloroethylene (79016). In this round, 89.7% of the laboratories were rated as being proficient. No significant changes in the samples provided to the laboratories or problems in the analyses were reported. The authors note that samples for round 116 have been sent out.