We reviewed methods of studies assessing restaurant foods' sodium content and nutrition databases. We systematically searched the 1964-2012 literature and manually examined references in selected articles and studies. Twenty-six (5.2%) of the 499 articles we found met the inclusion criteria and were abstracted. Five were conducted nationally. Sodium content determination methods included laboratory analysis (n = 15), point-of-purchase nutrition information or restaurants' Web sites (n = 8), and menu analysis with a nutrient database (n = 3). There is no comprehensive data system that provides all information needed to monitor changes in sodium or other nutrients among restaurant foods. Combining information from different sources and methods may help inform a comprehensive system to monitor sodium content reduction efforts in the US food supply and to develop future strategies.