As part of the recently passed Patient Protection and Affordable Care Act, chain restaurants with 20 or more locations nationwide are required to post calorie information on menus and menu boards in order to help consumers make healthier decisions when dining out. Previous studies that have evaluated menu-labeling policies show mixed results and the majority have been conducted in urban cities along the east coast. This study was the first to look at the effectiveness of menu labeling in a southwest population. The primary objective of this cross-sectional study was to determine if noticing or using calorie menu labels in a fast food restaurant was associated with purchasing fewer calories. A second aim of this study was to evaluate the relationship between socio-demographic characteristics and the likelihood of noticing and using menu labeling. Customer receipts and survey data were collected from 329 participants using street-intercept survey methodology at 29 McDonald's locations in low- and high-income neighborhoods throughout the Phoenix metropolitan area. The study population was 63.5% male, 53.8% non-Hispanic white, and 50.8% low-income. Results showed that almost 60% of the study sample noticed calorie menu labeling and only 16% of participants reported using the information for food or beverage purchases. Income was the only socio-demographic characteristic that was associated with noticing menu labeling, with higher-income individuals being more likely to notice the information (p=0.029). Income was also found to be associated with using menu labels, with higher income individuals being more likely to use the information (p=0.04). Additionally, individuals with a bachelors degree or higher were more likely to use the information (p=0.023) and individuals aged 36 to 49 were least likely to use the information (p=0.046). There were no significant differences in average calories purchased among those who noticed menu labeling; however, those who reported using calorie information purchased 146 fewer calories than those who did not use the information (p=0.001). Based on these findings it is concluded that calorie menu labeling is an effective public policy and that nutrition education campaigns should accompany national menu labeling implementation in order to make the policy more effective across all socio-demographic groups.