Dominant patterns and processes in rare bryophyte ecology are presented within the framework of current rarity theory. Available evidence suggests that bryophyte conservation should primarily consider the importance of establishment and habitat requirements for rare species. Preservation of rare and high quality habitats is essential. Future understanding of causes of rarity in bryophytes will benefit most by exploring the ecological drivers that allow species to expand their ranges. Comparisons of rare-common congeners, rare species throughout their range (not only where they are rare) and species currently experiencing range expansions or contractions are likely to yield the most robust and relevant data sets.