The results of the Proficiency Analytical Testing (PAT) Program, round 110, conducted in July 1992 were presented. The program was designed to offer quality control for more than 1,400 occupational health and environmental laboratories in over 15 countries by providing them with reference samples for analysis and verification upon return. In this round, results were submitted by 1,363 laboratories. Over 90% of the laboratories evaluated were rated overall proficient. Of 1,424 laboratories participating in the PAT program during rounds 107 to 110 for the period of October 1991 through September 1992, 8.6% were rated nonproficient. The solvents, metals, and asbestos (1332214) samples sent out in the PAT round 111 on October 1, 1992 were described.