In the increasingly consumer-driven food system, consumer preferences toward agricultural biotechnology have the potential to influence decisions about development and adoption of biotech crop varieties. Current knowledge about consumer attitudes toward biotech foods is largely based on a number of consumer surveys and a growing body of experimental auctions. This paper reports results of a market experiment designed to isolate the effect of the use of biotechnology on consumer choices between two otherwise identical products. Two related varieties of fresh-market sweet corn were grown, labeled, and sold side-by-side in nine participating grocery stores in the Philadelphia area. Sales data indicate a market share of biotech corn of about 45 percent, with store-specific shares varying between 10 and 80 percent. Over 700 surveys were collected in stores. Surprisingly, only 65 percent of respondents noticed that there were two types of corn for sale despite the labeling and merchandising, and 87 percent of the sample spent one minute or less choosing their corn. About half of the respondents had heard of biotechnology before, and 16 percent volunteered the biotechnology trait as an influence on their purchase decision. Approximately 40 percent of the sample purchased some of the biotech variety, with several respondents purchasing some of each.