North American lichens display recurring patterns of distribution that can be named, classified and analyzed. Past attempts at such classification systems have been used in various publications. A new system, expanding on previous works, was developed in the preparation of "Lichens of North America," a new reference work on the lichen flora of the continent scheduled to appear in the autumn of 2001. Interesting patterns and recurring disjunctions seen in lichens are relevant in discussions of North American phytogeography.

Key words: distribution, lichens, phytogeography