This dissertation provides a quantitative analysis of cultural ecology and social structure in a rural parish in Northwest Portugal. There is greater economic inequality, and greater social stratification than most ethnographers of Iberia have described. Chapter 1 introduces some of the material indications of wealth and land inequality in the community. Some households are shown to have much more land and dairy cattle than others. Chapter 2 discusses nickname behavior as a set of socio-cultural symbols for expressing an ideal of equality, which in some sense runs counter to material differences within the community. Chapter 3 analyses contemporary farming systems; showing that having different amounts of land determines each household's choice of technology. Each household operates its farm in a unique natural and economic environment, because of different access to the factors of production, especially land, but including labor and capital. Chapter 4 shows that patterns of technical change also depend on land supply. Larger farmers are the first to adopt new innovations, especially labor-saving devices. Chapter 5 demonstrates that, counter to common assumptions, land fragmentation is more pronounced on large farms than on smaller farms, but that for no farms is land fragmentation a barrier to agricultural production. Chapter 6 is a brief history of recent changes of land use. It shows that the most common land-use types, fields and forests, are somewhat interchangeable. Fields are converted to forest, and forest to field, depending on the economic environment of the owning household, and the natural environment of the land itself. Ecologically marginal land that is owned by large farmers is the most likely to be changed from field to forest, or from forest to field.