The background and current status of the Environmental Lead Proficiency Analytical Testing (ELPAT) Program were reviewed. The ELPAT Program was administered by the American Industrial Hygiene Association, NIOSH, and the United States Environmental Protection Agency (EPA). Proficiency test samples, consisting of real world paint chips, dusts, and soils, were sent on a quarterly basis to participating laboratories. Participation in the ELPAT Program was required by various environmental lead laboratory accreditation systems. The analytical results of the participating laboratories were compared to those of the selected reference laboratories. The acceptable performance range was +/-3 standard deviations of the statistically treated reference laboratory data. Laboratories were rated based on performance in four rounds of the ELPAT program. ELPAT Round 16 was sent to 384 laboratories in August 1996. A total of 365 laboratories submitted results. The relative standard deviations of the reference laboratories ranged from 6.3 to 11.8% for paint chips, 4.2 to 16.2% for soils, and 6.0 to 12.8% for dust wipes. The proportion of outliers in the participating laboratories ranged from 2.5 to 10.9% for paint chips, 4.3 to 8.9% for soils, and 4.2 to 8.2% for dust wipes. The lead measuring capacities of the participating laboratories did not vary significantly according to the sample preparation technique and method used. For some paint chip and dust wipe samples, flame atomic absorption spectroscopy yielded a significantly higher lead concentration than inductively coupled plasma atomic emission spectroscopy. The differences between these methods ranged from 6 to 16%. The authors conclude that successful performance in a proficiency testing program such as the ELPAT Program is required for accreditation by the EPA's National Lead Laboratory Accreditation Program.