Abstract Question: What are the responses of Racomitrium lanuginosum moss to altered snow-lie and sheep use? Location: A Carex bigelowii-Racomitrium lanuginosum heath on a Scottish montane plateau affected since 1986 by a fenced ski corridor. Methods: Permanent quadrats were set up along transects 45 m long perpendicular to the snow-fence. Cover was assessed over a 12-year period from 1990. Pellet-group clearance counts provided data on sheep usage between 1990 and 1996. Snow-lie was mapped in the springs of 1991-1996. Results: The snow-fence created a gradient in sheep use and altered the duration of snow-lie. At the start of monitoring Racomitrium cover was lower immediately adjacent to the fence, and after 12 years its cover was significantly reduced within 10 m of the fence. Further away from the fence Racomitrium cover was relatively stable. The loss of Racomitrium was correlated both with increased snow-lie and heavier sheep usage. Grass cover increased near the fence and was related to sheep use. Dicranum fuscescens had much different reaction to Racomitrium, increasing significantly near the fence. Conclusions: We found that changes in snow-lie and grazing pressure quickly brought about vegetation change in this montane ecosystem. Racomitrium was the most sensitive species to the changes in grazing and snow-lie caused by the fence, having the biggest initial changes. Loss of Racomitrium permitted increases of species more resistant to grazing including Dicranum fuscescens and grasses. Nomenclature: Stace (1997) for vascular plants; Smith (1978) for mosses.