Paint samples for Round 23 were prepared from paint chips collected from a variety of sites in North Carolina and Ohio, including a school, hospital, and warehouse. The chips were ground to a maximum particle size of 120 micrometers (um). Soil samples came from driplines around North Carolina residences. Soil samples were dried and then sterilized by heating the soil to 325 degrees F for a minimum of 2 hours, and finally sieved to a maximum particle size of 150 um. Round 23 dust wipes were prepared from dust collected from households in North Carolina and Milwaukee, Wisconsin. Following sterilization by gamma-irradiation, the household and post-abatement dust was sieved to 150 u m and gravimetrically loaded on a premoistened PaceWipe, which has been shown to meet ASTM E 1792 specifications. The loaded wipes were stored under refrigeration until shipment as an antimicrobial measure. Also, it was recommended that dust wipe samples be refrigerated until the laboratory analyses were performed, as an additional precaution to reduce/prevent the growth of mold. A total of 352 laboratories was enrolled for the twenty-third round of the ELPAT Program with 328 laboratories (93%) submitting results. Table I lists summary statistics of reference laboratories for each matrix and sample number. Agreement among reference laboratories using a variety of sample preparation techniques and analytical methods is demonstrated by relative standard deviations (RSDs) ranging from 6.2 to 9.2 percent for paint chips, 5.5 to 11.9 percent for soils, and 7.3 to 11.6 percent for dust wipes. The RSDs are similar to the findings on previous ELPAT rounds.