Experimental auction markets were designed and used to investigate consumer preferences for sandwiches produced with meat from pigs treated with porcine somatotropin. A second-price, sealed-bid auction procedure was used to determine willingness to pay to exchange a pork loin sandwich with leaner meat from pigs treated with somatotropin for a similar sandwich with meat from untreated pigs. The research was conducted using a sample of 114 undergraduate students in Iowa, Arkansas, Massachusetts, and California. At the end of the experiment 33 of 58 subjects would not bid to change their leaner pork for typical pork, whereas 15 of 56 subjects would not bid to change their typical pork for leaner pork. The results suggest a preference for leaner meat from the treated pigs, but also the potential for niche markets for meat and meat products from untreated pigs.