An archaeological excavation was carried out by Oakford Archaeology between November 2020 and February 2021 in the Chapter House and the Chapel of the Holy Spirit, Exeter Cathedral, Exeter. The below-ground works were accompanied by building recording undertaken by the Cathedral Archaeologist. The excavation in the Chapter House revealed a garden soil which had formed prior to the construction of the standing building. This had been disturbed in the 19th or 20th century during the refurbishment of the Chapter House. Sampling below this layer revealed a sequence of late Roman and post-Roman deposits which was the subject of programme of soil analysis and have been reported separately. The reputed grave of Serlo, the cathedral's first Dean who died in 1231, was found and his skeleton re-examined, and no other burials were encountered. Reports on the large collections of medieval floor-tiles and animal bone are appended. The accompanying study of the standing building provided new records of the geology and phasing of the internal elevations prior to the replastering of the lower parts. It found fresh evidence for the form of the early 13th-century building, including a newly identified portion of the clerestory in its western bay which provides further evidence for the form of the primary timber vault. Excavation in the Chapel of the Holy Spirit, accompanied by the stripping of cement from its walls, provided much new information about the architectural development of this poorly understood space. The interpretation that this area was formerly a slype can now be discarded; before the late 13th century the ground consisted of a steeply sloping garden soil. When the Chapter House was built in the 1220s on the adjacent plot to the south, it had substantial buttresses which projected into this area but these were removed when the chapel was formed. Its construction entailed enclosing the space with an east wall, then infilling the area with a raft of unmortared volcanic stone rubble, on which a tiled floor was laid. The chapel was provided with stone benches, the northern one being created by crudely cutting back the ashlar of the south tower. The excavation confirmed that, rather than dating from c.1500, the chapel was built in the late 13th or early 14th century, as suggested in the Archaeological Assessment of 2020. The primary floor level was subsequently lowered slightly and replaced by a sloping floor, which would have served the Consistory Court of the...