This report presents the results of a mixed-methods, summative evaluation of Zambia’s First 1000 Most Critical Days Programme (MCDP). The MCDP is a bundled, multi-sectoral programme that aims to reduce stunting in Zambia by 50% by focusing on the most critical period for stunting: pregnant and lactating mothers, and children under 2 years of age. The programme focuses on bringing to scale a strategic subset of routine evidence-based interventions proven to reduce stunting: deworming and vitamin A supplementation; family planning; growth monitoring; iron and folic acid supplementation; iodised salt, micronutrients, and breastfeeding; fortified staples and specialised nutritional products; a mother- and baby-friendly hospital initiative; and management of severely malnourished children (National Food and Nutrition Commission of Zambia [NFNC], 2011). These interventions are supplemented by a range of trainings and behaviour change components designed to take advantage of potential complementarities between child health and improved maternal knowledge, WASH practices, and nutritional intake. The programme is led by the Zambia Food and Nutrition Commission (NFNC) and it involves the Ministry of Health (MoH), Ministry of Education (MoE), Ministry of Agriculture, Livestock and Fisheries (MoA), the Ministry of Community Development and Social Welfare (MCD), and the Ministry of Local Government and Housing (MLGH). CARE International is the main technical assistance and fund management partner and the MCDP is funded by the Scaling Up Nutrition network (SUN) in Zambia. (359 pages)