The term rural area is immediately understood by everybody. However, the creation of an objective, unequivocal definition of the countryside appears to be a tricky, even impossible task. Population density is a criterion most often used to define the boundary between rural and urban areas. The article presents new methods for definition of rural areas at two hierarchical levels — the local level (municipalities) and a territorial unit (district, region). The methods are based on the construction and the use of membership function of rural and urban areas.