A phylogenetic hypothesis based on nuclear ITS sequence data is presented for the family Physciaceae, based on various representatives of foliose and fruticose groups and a number of species selected from the crustose genera Rinodina and Buellia s.l. The analysis supports the monophyly of the Physcia- and the Buellia-groups. This is in agreement with existing morphological evidence, particularly ascus characters. The Physcia group in the analysis includes the genera Anaptychia, Heterodermia, Hyperphyscia, Mobergia, Phaeophyscia, Phaeorrhiza, Physcia, Physconia, Rinodina, and Rinodinella, while the Buellia group includes Amandinea, Buellia and Diploicia. The genera Physcia, Phaeophyscia, Phaeorrhiza and Rinodinella were well supported as monophyletic groups. The support for Physconia is low. Rinodina and Buellia are not supported as monophyletic genera. In agreement with ascus and ascospore characters, Buellia lindingeri is placed within the Rinodina group, close to R. lecanorina. The genus Amandinea as currently circumscribed was not supported as a monophyletic group. The analysis confirms results from other lichen families that foliose members have evolved more than once from crustose lichens. Rinodina and Rinodinella species without chemical compounds in their thalli form the sister group to Phaeophyscia, and both groups form a monophyletic assemblage. A more detailed analysis of the Physcia group is presented. Whilst several of the foliose genera were well supported, there is only poor support for traditionally accepted crustose genera. The taxonomic implications of these findings are discussed. (C) 2001 The British Lichen Society.