The Neolithic site of the Knowe of Rowiegar chambered cairn, Orkney, was excavated in 1937 as part of a campaign that saw the excavation of various chamber cairns on the island of Rousay, Orkney (Davidson & Henshall, 1989). Osteological and isotope research undertaken in recent years has reignited interest in the site. The research presented here focuses on mortuary practices, principally through histotaphonomic analysis. Human remains at Rowiegar were characterised by disarticulation, disorder and fragmentation (Hutchison et al., Proceedings of the Society of Antiquaries of Scotland, 145, 41–86, 2015), as is commonly observed in Neolithic Orkney. In recent years, histological analysis has become more widely used in reconstructing mortuary treatment. This relies on the degree and nature of bacterial attack, often termed bioerosion, and other modifications to bone microstructure as a proxy for early post-mortem treatment. Histological analysis was undertaken on 13 of the 28 individuals from the Rowiegar site. The results presented diverse patterns of bioerosion in the bone microstructure suggesting different mortuary practices. Furthermore, these results suggest that remains were placed in the chambered cairn at different stages of decomposition, with some individuals buried immediately after death and others likely subject to a more complex, multi-stage mortuary rite. There remains uncertainty about the origins of bacterial bioerosion in bone, and future experimental work may necessitate interpretative revision. However, based on current understanding, the research provides a new perspective on mortuary practice at Rowiegar, evidencing diverse, and sometimes complex, pre-depositional mortuary practices.