|Notes:||Prior to its excavation between 1932 and 1934, the Midhowe stalled cairn was a long, grass-covered mound about 20 metres from the southern shore of Rousay. It measured around 2.7m high with a row of slabs projecting from the surface.|
Excavation was instigated by the landowner Walter Grant, who, along with J. Graham Callander, gradually revealed the remains of a stalled burial chamber, described at the time as looking like “a long narrow byre, with twelve stalls on each side, separated from one another by short trevisses of slabs”.
Aligned SE-NW, the cairn is rectangular in plan with rounded corners and is 32.5m long by 13m wide. It is bounded by an elaborately built wall-face with another 1.4 to 2.3m within.
Access was by a 3.9m long and 0.8m wide entrance passage in the south-eastern end of the structure. This had been blocked at both ends, the outer face flush with the exterior of the cairn.
The chamber is 23.4m long by 2 to 2.2m wide, divided by pairs of orthostats into twelve compartments from 1.2m to 2.1m long.
Low “benches” had been constructed along the north-eastern side of the chamber, in the fifth to the eleventh compartments.
The remains of at least 25 human skeletons were found, mostly lying on the benches. Some were crouched but others were very incomplete, with the bones in apparently gathered heaps. No human remains were found in the four outermost compartments.
Animal bones were mixed with the human remains.
The excavators found that the chamber had been filled with loose slabs, among which were animal bones and some stone tools. Two crouched skeletons in the fourth compartment were 1.2m above the floor level, one in a roughly made cist.
The filling was interpreted as collapsed roof and cairn material, but it is likely that at least the lower part had been deliberately introduced to seal the chamber.
At the north-western end of the cairn was evidence of secondary occupation at a higher level with a passage leading to the chamber about 0.9m above floor level. The wall of the innermost six compartments is now only 1.7m high, and, at this level, on the north-eastern side are the remains of a later wall set back 0.3 to 0.8m from the chamber walls.
This addition is suggested to be the reason the height of nine inner orthostat dividers and the back slab were reduced in height. Other secondary additions were also found against the northern corner, including a cist-like box.
Two walls, with an average width of 1.4m and up to 1.2m high, extend from the northern and eastern corners of the cairn. The excavators followed the northern wall for 21m and found a carefully constructed gap, 0.6m wide, 11 metres from the cairn. The eastern wall, which was traced for 13.7m, had a similar gap one metre from the cairn.
Both walls had foundations 0.2-0.3m below the base of the cairn and where they abut the cairn its walls are undisturbed. The date and role of the two walls is not known.
After excavation, the monument was taken into Guardianship and enclosed in a stone building.
The human remains
In all, the remains of 25 individuals – including adults, adolescents and children as young as two years old – were identified. 
On each of the “benches” along the north-eastern side , except the innermost, were the remains of two to four skeletons. Nine of these were crouched, except one which appeared to have been in a sitting
“[I]n the south-east corner were remains of the skull of an adult … the vertebrae lay along the wall and the knees were drawn up in front”. 
Below one “bench” was a deposit said to represent two adults and a child, and on the floor on the opposite side of the chamber were “the scanty remains of an adult skeleton” . It is possible these had actually started out on top but ended up on the floor after the collapse of the “benches” .
As well as articulated remains, there were also four heaps of bones, each suggested to represent one individual, and which are presumably the result of the later manipulation of skeletal material:
“[T]he collected remains of the skeleton of an adult male, the limb bones being placed against, and parallel to, the wall, with part of the skull above them.” 
As well as apparently complete deposits, there were also fragmentary remains, including one whole and two fragmentary skulls. The skulls of two articulated skeletons had been set upright to face the centre of the chamber.