Summary.The settlement complex on Longbridge Deverill Cow Down in west Wiltshire comprises two major farmsteads, with their associated trackways and field systems, which were in use from the 8th to the 2nd century BC. The excavations, between 1956 and 1960, could only sample Enclosures II and III, whose ditches turned out to be relatively late features belonging to the larger and longer lived of the two farms. However, by good fortune, the interior areas excavated contained the very well‐preserved post‐holes of no less than four successive great round houses, the largest up to 60 feet (18.30 m.) in diameter, with masses of surviving structural evidence, pottery and other finds. This article describes and discusses the latest and best preserved of the great houses, House 3 of the end of the 6th century, and it attempts to throw new light not just on the construction and internal lay‐out of these huge structures, but also the manner in which they may have been used, domestically and ceremonially, by their inhabitants at the end of the Late Bronze and beginning of the Iron Age in W