Stone formers trying to limit dietary sodium may be unable to give up fast food. For the classic American hamburger, it is unclear if lower sodium preparations of this item are available and how this could affect sodium intake. We determined the impact of careful selection at national chains. Nutritional guides for 14 national chains were analyzed for all beef-based burgers and french fries. A meal was defined as 1 burger and an order of fries. The daily sodium limit (recommended daily sodium allowance [RDA]) was considered to be 2,300mg. The maximal sodium reduction was defined as the difference between the highest and lowest sodium-containing meals. The Kruskal-Wallis test with Dunn's method was used to compare food items among the chains. Of the total 263 different burgers and 74 different fries, median sodium was 1130mg (range 180-3520) and 565mg (range 30-1480), respectively. Mean sodium for burgers at individual chains ranged from a low of 590mg to a high of 1721mg (P<.001). The mean sodium for fries at individual chains ranged from a low of 245mg to a high of 947mg (P<.001). Post-hoc testing revealed 26 significant differences between pairs of restaurants for sodium content of burgers with P<.05 for each. The median maximal sodium reduction among the different chains was 1925mg. Depending on the chain, sodium content of 1 meal could be reduced by as little as 830mg (36% RDA) or as much as 3360mg (146% RDA) by careful selection. Stone formers should be aware of significant variation in sodium content of burgers and fries among chains and within a chain. Wisely selecting just 1 fast-food burger meal can significantly reduce sodium intake.