Genetically modified (GM) foods have generated intensely negative consumer attitudes in many countries, particularly in Europe. Several expert reviews indicate that safety concerns regarding GM foods appear largely unfounded, but expert opinions have been insufficient to greatly change public sentiment. Even so, antipathy toward the concept of genetic modification will not necessarily translate into consumer resistance to such foods once introduced into the market.The experiments reported here were undertaken to determine how consumers in a range of countries with highly negative public perceptions of GM technology might react toward GM food products that offer clearly stated consumer benefits if introduced into their markets. Classic economic theory postulates that consumers seek to maximize self-interest in the presence of pecuniary or other advantages6. Ample evidence exists that consumer attitudes, and even stated behavioral intentions, may not translate into purchase behavior.We set up real roadside fruit stalls based on a choice modeling experimental design. Experimental choice modeling has been widely used as a method for determining behavior based on subjects making choices from sets of product options put before them9. What makes our study highly novel is that the choices were real in a genuine shopping situation, rather than being made under circumstances where the subjects knew that their choices were being observed. Our intention was to minimize the possibility of social desirability bias10 influencing the results.We placed on sale conventional fruit labeled as 'organic', 'spray-free genetically modified', or 'conventional', or appropriate translations of same in the prevalent local language at each site, at varying price levels. The price for each fruit category was set at one of three levels: the median market price in that locality, median plus 15% or median minus 15%. A parsimonious main effects balanced fractional factorial design was used to generate nine price and fruit offerings (Table 1). Research assistants fluent in the local language operated the stalls, which were set up on the outskirts of urban areas in New Zealand (Queenstown), Sweden (Ystad, Skåne), Belgium (near Brussels), France (Paris), Germany (Koblenz, Rheinland-Pfalz) and the UK (Berwick-upon-Tweed). We avoided locating adjacent to farms or orchards to minimize the risk of upsetting local producers. If customers asked about the spray status of different fruit types, verbal explanation was provided that the organic fruit could have been sprayed with 'Bacillus thuringiensis (Bt) organic spray' and that the spray-free GM fruit was from plants incorporating the Bt gene, making spraying unnecessary. (Less than 5% of customers over the six experiments enquired.) In each case, the experimental set of offerings (Table 1) changed after ~50 customers, yielding ~450 observations from each country. In accordance with University of Otago Ethics Approval requirements, customers were informed of the experiment (verbally, or by using a display card if other customers were present) after they had made their selection, but before money changed hands. A main reason for using roadside fruit stalls, rather than street market or other walk-in situations, was to minimize the risk of contamination of customer intentions through overhearing reactions from customers newly aware of the 'candid camera'-like stratagem.