The report on partial rescue excavations of the Collfryn enclosure between 1980–82 presents a summary of the first large-scale investigation of one of the numerous semi-defensive cropmark and earthwork enclosure sites in the upper Severn valley in mid-Wales. Earlier prehistoric activity of an ephemeral nature is represented by a scattering of Mesolithic and Late Neolithic or early Bronze Age flintwork, and by a pit containing sherds of several different Beaker vessels. The first enclosed settlement, constructed in about the 3rd century bc probably consisted of three widely-spaced concentric ditches, associated with banks of simple dump construction, having a single gated entranceway on the downhill side. It covered an area of about 2.5 ha and appears to have been of a relatively high social status, and appropriate in size for a single extended-family group. This was subsequently reduced in about the 1st century bc to a double-ditched enclosure, by the recutting of the original inner ditch and the cutting of a new ditch immediately outside it. The habitation area between the 3rd and 1st centuries bc probably focused on timber buildings in the central enclosure of about 0.4 ha, whose gradually evolving pattern appears to have comprised between 3–4 roundhouses and 4–5 four-posters at any one time. Little excavation was undertaken between the outer ditches of the first phase settlement, but these are assumed to have been used as stock enclosures. A mixed farming economy is suggested by cattle, sheep/goat and pig remains, and remains of glume wheats, barley and oats. Industries included small-scale iron and bronze-working. The Iron Age settlement was essentially aceramic, although there are significant quantities of a coarse, oxidized ceramic probably representing salt traded from production centres in the Cheshire Plain. The entranceway was remodelled in about the late 1st or early 2nd, century AD by means of a timber-lined passage linked to a new gate on the line of the inner bank. There is equivocal evidence of continued occupation within the inner enclosure continuing until at least the mid-4th century AD, possibly at a comparatively low social level, associated with domestic structures of uncertain form sited on earlier roundhouse platforms, and including some four-posters and possible six-posters. Drainage ditches were dug across parts of the site during the Medieval and post-Medieval periods, which were associated with various structures, including a corn-drying kiln inserted into the inner enclosure bank in the 15th century.