The oldest still visible traces of domestic architecture in Pompeji show two construction techniques: opus quadratum (ashlar masonry) and opus africanum (limestone framework). These techniques were applied together in the same building, each for a specific purpose. Whereas ashlar masonry was always used in a consistent manner, the walls of limestone framework display a greater variety, which can be classified on the basis of construction techniques. This research has taken also into account the composition of the clay mortar which is typical for this period. After a relative chronology was established the evolution of early domestic architecture was traced through various stages of development. The best known example of domestic architecture from this early period is the House of the Surgeon, which was one of a small group of houses for the elite of that time. Most li-mestone framework houses from the period are decidedly smaller and occur in two different types, probably meant for the middle class. The first type displays the same general characteristics of the elite houses on a smaller scale. The other consists of a plan with standard layout and dimensions. These types, both the atrium houses of the elite and the standard small houses do not represent the beginning of a development, but an advanced stage, which is documented in Pompeii from the beginning of the fourth century BC.