This paper describes a small Mesolithic structure from the Cairngorm Mountains, Scotland. Excavations at Caochanan Ruadha identified a small oval structure (c. 3 m×2.2 m) with a central fire setting, in an upland valley (c.540 m asl). The site was occupied at c. 8200 cal BP and demonstrates hunter-gatherer use of the uplands during a period of significant climatic deterioration. The interpretation of the structure is primarily based on the distribution of the lithic assemblage, as the heavily podsolised soils have left no trace of light structural features. The lithic assemblage is specialised, dominated by microlith fragments, and functional analysis has identified different uses of different areas inside the structure. The identification of small, specialised Mesolithic sites is unusual and this paper will discuss the evidence for the presence of the structure and its use, compare it to other Mesolithic structures in Britain and highlight some methodological implications.