Many different indexes have been developed to describe diet quality. Some are based on the nutrient content of food and specific components that affect metabolic indicators of adverse outcomes. Some indexes identify foods that are characteristic of particular cuisines, whereas other indexes use a mix of foods and nutrients as their basis. The most recent index (NOVA) uses the presence of additives as a marker for classification. Some indexes are intended for health promotion purposes, whereas others are used in regulatory activities, such as front-of-pack labeling. This article examines the literature to determine what information is available on the ability of any index to predict important outcomes such as mortality. Articles were selected if they compared 2 or more indexes or if they described outcomes for any index related to the UK Office of Communication nutrient profiling algorithm or the recently developed NOVA index. Few comparative articles were found. All of the indexes predicted mortality, heart disease, or cancer to some extent. The associations were small and could be due to residual confounding or attenuation due to measurement error. Given the similarity in results across the indexes, other criteria would need to be used when deciding which index to select for any specific context.