On February 28, 1992, the Centers for Disease Control and Prevention and the Health Care Financing Administration (HCFA) mandated that all regulated laboratories must participate in a HCFA-approved proficiency program. The Wisconsin State Laboratory of Hygiene (WSLH) has approved PT programs in all areas of laboratory testing and offers proficiency testing (PT) to more than 4,000 laboratories throughout the United States. Data are shown for four specialties of testing for the first two PT events of 1994. Results indicate that a significant number of newly enrolled laboratories, boarding on 10%, are likely to fail in the initial PT event. However, nearly three-quarters of these were able to correct the problem before the second event. The benefits of PT, as a quality assurance tool, presumably will be demonstrated in successful long-term performance.