Objective: Evaluate effect of low-carbohydrate claims on consumer perceptions about food products' healthfulness and helpfulness for weight management. Design: Experiment in which participants were randomly assigned 1 of 12 front-of-package claim conditions on bread or a frozen dinner. Seven of the 12 conditions also included Nutrition Facts (NF) information. Setting: Internet. Participants: 4,320 members of a national on-line consumer panel. Intervention: Exposure to images of a food package. Main Outcome Measures: Ratings on Likert scales about perceived healthfulness, helpfulness for weight management, and caloric content. Analysis: Mean ratings by outcome measure, condition, and product were calculated. Ratings were also used as the dependent measure in analysis of variance models. Results: Participants who saw front-of-package-only conditions rated products bearing low-carbohydrate claims as more helpful for weight management and lower in calories than the same products without a claim. Those who saw the bread with low-carbohydrate claims also rated it as more healthful than those who saw no claim. When the NF label was available and products had the same nutrition profile, participants rated products with low-carbohydrate claims the same as those with no claim. Conclusions and Implications: Consumers who do not use the NF panel may interpret low-carbohydrate claims to have meaning beyond the scope of the claim itself. (Contains 2 tables.)