Resistant starch has received a lot of attention for its potential to exert a healthy impact on the gut and certain members of its resident microbiota, particularly through enhanced butyrate production. However, resistant starch is a broad category that encompasses several structurally different starches. While all resist digestion by human enzymes, they differ in their effects on the microbiota. Individual variation in microbiota composition also has a substantial influence on butyrate production. Research on this interaction between resistant starch and the microbiota is using in vitro fermentations, cross-over design clinical trials and mouse studies with isotopically labeled starch. These studies are demonstrating that more personalized approaches are needed for finding resistant starch or other fiber that will promote a healthy gut.