This stage of Pueblo culture dates from approximately A.D. 500 to 700. BMIII is a continuation and elaboration of the BMII adaptation. During BMIII, there appear a number of cultural innovations, but many of the ways of BMII also continue. There is good evidence that population has increased by BMIII, and that villages have become larger. There are many more BMIII sites than BMII sites, and they are spread over a wider area (for example, there are a few BMIII sites in the Flagstaff area). At some BMIII sites, one or a few exceptionally large pit structures are found. These are interpreted as some form of communal gathering place, perhaps the earliest expression of a great kiva. These structures suggest that BMIII societies were socially integrated at a level not seen in BMII, i.e., there was some form of intra- or even inter-village cooperation regarding important decisions and ceremonies. Changes during BMIII (compared to BMII) involve:

Construction of larger and more complex pithouses. Many BMIII pithouses have large alcoves or vestibules; raised ridges in the floor dividing the house into sections; slabs lining the walls of the pithouse; and a large hearth in the center of the pithouse.

The bow and arrow is introduced (throwing spears or darts also continue to be used, but the bow and arrow is added as a weapon)

Beans are added to the diet, to supplement the corn and squash that were cultivated in BMII.

A lack of cranial deformation continues, that is during BM III babies are carried in cradle boards in such a way that their heads are not deformed.

Many of the same material items listed above for BMII continue to be used, though there is some elaboration in the style of basketry and woven items. For example, sashes, sandals, bags, baskets, and other woven objects achieve a high degree of technical and artistic excellence.

Turkeys are raised in BMIII, for food and feathers

There are some relatively large village sites during BMIII. An example is a site called Shabik'eschee village, on the rim of the south side of Chaco Canyon. This site had 18 pithouses, one exceptionally large, circular pit structure (often interpreted as a "great kiva"), and over 50 storage pits. Tree-ring dates place most of the construction and occupation of Shabik'eschee village at about A.D. 550, with use or occupation continuing to about A.D. 700. It is not entirely clear how many of the 18 pithouses were occupied at any given time, and the "great kiva" may date toward the end of the occupation. However, the number and distribution of storage pits suggests that large numbers of BMIII people did periodically congregate at Shabik'eschee. The peak population of Shabik'eschee has been estimated at about 77 people, a figure far larger than the "average" BMIII settlement of 5 to 15 people, or 1 to 3 families (Wills and Windes, American Antiquity Vol. 54 No. 2). Why some groups of BMIII people chose to aggregate into larger villages like Shabik'eschee is not known, but it has been suggested (Wills and Windes) that such villages might have formed to allow increased food storage and year-round residence during years when agricultural surpluses and/or pinyon nut harvests were especially good. These larger villages in turn may have created the need for larger and more integrative ceremonial associations and activities, which could account for the presence of "great kivas." However, there is no evidence that there were important or powerful individual leaders during this time. Most decisions were probably made by consensus of household heads, and whatever political organizations might have arisen during times of stress were probably short-lived and confined to the solution of particular problems.