The sandstone outcrops of The Weald and Cheshire have been major national strongholds for the endangered Slender Thread-moss (Orthodontium gracile), a rare plant in Europe. But recent searches in Cheshire have raised new concerns over its future. A total of 11 days of surveying in Alderley Edge and The Peckforton Hills found the plant at only a single location and in very small quantity. It could not be refound at any of the three locations where it had been seen during a survey in 1999-2000. The rockface where it was seen at Alderley Edge in 2000 has now dried out and moss cover generally is much reduced. At the two locations where it was seen in 1999 in The Peckforton Hills, the physical habitat conditions appeared largely unchanged. It seems likely that competition from the non-native O. lineare is a problem. This moss appears to be capable of occupying the entire niche space of O. gracile and, in Cheshire at least, is common at all sites where its rare cousin has been known. Worryingly, the survey results cast some doubt on the long-term, or even short-term, survival of O. gracile in North-west England. And if O. lineare is the problem, there is little that can be done to prevent its loss.