Antimicrobial sprays applied using a modified inside-outside birdwasher to reduce Salmonella typhimurium and total aerobic bacteria on prechilled chicken carcasses were evaluated in a poultry processing pilot plant. Four chemicals, including trisodium phosphate (TSP, 10%), lactic acid (LAC, 2%), cetylpyridinium chloride (CPC, 0.5%), and sodium bisulfate (SBS, 5%) were selected to be tested as antimicrobial agents. Each chicken carcass was inoculated by spraying the outside and inside of each carcass with S. typhimurium at 10(5) CFU per carcass. The inoculated carcasses then were passed through the birdwasher and sprayed with selected chemicals at 35 degrees C at a pressure of 413 kPa for 17 s. After a 60-s setting time on a shackle line, the carcasses were sprayed with tap water to rinse off chemical residue. All the chemical treatments reduced Salmonella on the chicken carcasses by approximately 2 log10 CFU per carcass. Total aerobes on the chicken carcasses, however, were reduced by 2.16, 1.66, 1.03, and 0.74 log10 CFU per carcass after spraying with 0.5% CPC, 5% SBS, 2% LAC, or 10% TSP, respectively. Spray treatments of both SBS and LAC caused slight discoloration in part of the chicken skin. The most effective antimicrobial spray treatment for reducing both Salmonella and total aerobes on prechilled chicken carcasses was 0.5% CPC.