An operational definition for "rural area" is pivotal if proposals, policies and decisions aimed at optimising the distribution of resources, closing the gap on inequity between areas and raising standards of living for the least advantaged populations are to be put in place. The concept of rurality, however, is often based on alternative and conflicting definitions, requiring clarification of the underlying theoretical model. Traditionally a geographical area has been classified as rural by taking into account either the number of inhabitants or population density. Two kinds of problem are raised with this approach, however, namely: it is inherently difficult to describe such a complex concept as rurality with a single variable: and reducing the concept down to a rural/urban dichotomy by setting a non-universal cut-off point does not usually provide an accurate account of reality. Within the context of the rural urban continuum, this paper has devised a rurality index for Spanish municipalities based on the 1991 Population, Housing and Household Survey. The index was built on a principal components factor analysis, giving rise to a single factor that is correlated to the aging of the population, economic dependency, farming, livestock or fishing-related employment, habitability of housing and population density. A score to each municipality was allocated. This index can be regularly updated thus enabling the progress of the concept of rurality to be monitored in our setting over time and then compared with other countries using the same methods.