Context: Dietary intake research has increasingly focused on improving diet quality in low- and middle-income countries (LMICs). Accompanying this is the need for sound metrics to assess diet quality. Objective: This systematic literature review aims to describe existing diet quality indices for general populations and highlights recommendations for developing such indices for food system research in LMICs. Data sources: Three electronic databases were searched for papers published between January 2008 and December 2017. Data extraction: Articles published in English and describing the development of an index to measure overall diet quality, irrespective of whether they were for high-income countries or LMICs, were included. Data analysis: Eighty-one indices were identified, over two thirds were based on national dietary guidelines from high-income countries. Of the 3 key diet quality dimensions, "diversity" was included in all 18 indices developed for LMICs, "moderation" was captured by most, and "nutrient adequacy" was included 4 times. Conclusions: Indices need to be developed that include all dimensions, include foods and/or food groups rather than nutrients, use an optimal range for individual components in the score, and express the intake of healthy and unhealthy components separately. Importantly, validation of the index should be part of its development. 2019 The Author(s) 2019. Published by Oxford University Press on behalf of the International Life Sciences Institute.