The status as of April 1997 of the Environmental Lead Proficiency Analytical Testing (ELPAT) Program was discussed. Participating laboratories were given paint chip, soil, and dust wipe lead (7439921) samples for analysis. The analytical results of the participating laboratories were compared to those of reference laboratories. The acceptable performance range for the participating laboratories equaled the mean +/-3 standard deviations of the statistically treated reference laboratory findings. Of the 392 laboratories enrolled in Round 18 of the ELPAT Program, 369 submitted results. Among the reference laboratories, the relative standard deviations (RSDs) ranged from 6.1% to 8.5% for paint chips, 5.0% to 11.8% for soil samples, and 5.1% to 9.3% for dust samples. The percentage of outliers among the participating laboratories varied from 3.3% to 4.7% for paint chips, 3.9% to 8.1% for soil samples, and 2.7% to 6.7% for dust wipes. No significant differences were determined in the ability of various analytical methods to quantify lead concentrations in paint chips, soil samples, and dust wipes. However, for paint chip samples, the use of anodic stripping voltametry (ASV) had a significant, positive bias over inductively coupled plasma atomic emission spectroscopy (ICPAES). For soil samples, ASV had a significant, positive bias over flame atomic absorption (FAA), which in turn had a positive bias over ICPAES. For dust wipe samples, ASV had a significant, positive bias over ICPAES and FAA, while FAA had a positive bias over ICPAES. NIOSH ELPAT studies determined that bias among instrumental methods used by the participating laboratories ranged from 2% to 26%. Successful completion of the ELPAT Program was required for accreditation by the National Lead Laboratory Accreditation Program. The ELPAT Program was open to all interested laboratories.