Women of reproductive age (WRA)1 are often nutritionally vulnerable because of the physiological demands of pregnancy and lactation. Requirements for most nutrients are higher for pregnant and lactating women than for adult men (National Research Council, 2006; World Health Organization [WHO]/Food and Agriculture Organization of the United Nations [FAO], 2004). Outside of pregnancy and lactation, other than for iron, requirements for WRA may be similar to or lower than those of adult men, but because women may be smaller and eat less (fewer calories), they require a more nutrient-dense diet (Torheim and Arimond, 2013)2 . Insufficient nutrient intakes before and during pregnancy and lactation can affect both women and their infants. Yet in many resourcepoor environments, diet quality for WRA is very poor, and there are gaps between intakes and requirements for a range of micronutrients (Arimond et al., 2010; Lee et al. 2013). These vulnerabilities and gaps in diet quality have been recognised for a long time. However, despite decades of appeals to improve women’s diet quality and nutrition, there has been little programmatic action. Historically, one major impediment has been a lack of effective platforms and programmes reaching adolescent girls and WRA outside of prenatal care. A lack of indicators to allow for assessment, advocacy and accountability has been another constraint. The Minimum Dietary Diversity for WRA (MDD-W)3 indicator defined and described in this document is a food group diversity indicator that has been shown to reflect one key dimension of diet quality: micronutrient adequacy, summarised across 11 micronutrients (Martin-Prével et al., 2015)4 . The indicator constitutes an important step towards filling the need for indicators for use in national and subnational assessments. Such indicators must be relatively simple to collect and suitable for large surveys5 .