Purpose:To encourage sustainable consumer practices, public policy makers introduce new ecological measures, including mandatory programmes that require companies to provide environmental information about their products, even if the information is not flattering. Few academic studies consider the potential impacts of such mandatory eco-labels on consumer behaviour; the purpose of this paper is to seek to identify conditions in which a generalized eco-label in stores might modify consumers’ purchase choices.Design/methodology/approach:Two quasi-experimental studies (n=333, 126) manipulate environmental information with a simple, traffic light – shaped eco-label. The measures focus on respondents’ choice or purchasing intentions, perceptions of the environmental harmfulness of each product, and individual characteristics (i.e. environmental concern, price sensitivity, familiarity with environmental information about the product category).Findings:The presence of an eco-label influences consumers’ beliefs about products’ environmental harm and thus choice. The effect of perceived harmfulness on choice is moderated by environmental concern and price sensitivity, though combined effects arise for only one of the two product categories tested (dish soap, not yoghurt). With a third product category (paper towels), Study 2 confirms the influence of familiarity with environmental information.Research limitations/implications:Familiarity with environmental information accounts for some differences across product categories, but other factors also come into play. These results must be interpreted carefully due to the use of a fictive eco-label.Originality/value:This paper examines the potential effects of a generalized, mandatory programme. It also addresses the lack of consistent label effectiveness across product categories, with a possible explanation based on perceived familiarity with environmental information.