Abstract For many years, the supply chain managers of large supermarkets and restaurant corporations have been conducting animal welfare audits of farms and slaughter plants. Some programs have been more effective than others. This case history describes the early implementation of a highly effective program for auditing animal welfare in slaughter plants. The lessons learned from the implementation of this program in 1999 are still relevant today. There were four major factors that made this welfare auditing program effective. They were: (1) corporate management became motivated to improve conditions in the slaughter plants after they visited plants that had severe animal welfare problems, (2) the welfare standards used to audit the beef and pork plants were simple and easy to understand. They provided clear guidance on conditions that would result in a failed audit, (3) more than one commercial company enforced the same standards at the numerous slaughter plants, and (4) there was an emphasis on repairing existing facilities and improving management instead of buying lots of expensive new equipment. There were only 3 plants out of 75 where expensive renovations were required. This case history will also discuss how veterinarians and management consultants can help food animal supply chain managers implement effective programs that will improve animal welfare. Practical commercial animal welfare assessments will need to be simpler than assessments used for research. Information © The Author 2023