This paper discusses the local knowledge of the Muong in Xe II Village in northern Vietnam. The Muong are one of 53 ethnic minority groups in Vietnam. Xe II Village is located in the highlands, far from urban centres. Its inhabitants are mainly subsistence farmers. This paper examines the role of local knowledge in villagers' land-use systems. The paper focuses on local knowledge in wet rice cultivation and animal husbandry. Wet rice cultivation is a long- standing tradition of the Muong people, who have benefited from scientific and technical expertise. However, they have preserved traditional techniques in land preparation and irrigation, with positive effects on soil fertility and protection from soil erosion. Although many villagers use new rice strains, they have carefully selected different rice varieties to suit plots located in different conditions. The villagers continue to use compost and some traditional materials against rice pests and rats, in addition to chemical fertilizer and pesticide. Just as in wet rice cultivation, people have preserved and developed local knowledge concerning animal husbandry. They have flexibly combined rice farming and fish rearing in the same fields. Traditional rules strictly enforced by villagers on the use of natural resources and grazing areas have protected the sources of feed for cattle. The paper concludes that the traditional knowledge of the Muong in Xe II Village has made valuable contributions to community development. The knowledge has been preserved and handed down from generation to generation in families, family clans and villages, through exchanges during farming activities, leisure time, and meetings. The paper also finds that each gender possesses different local knowledge.