Chloroplast DNA regions (trnL(UAA) - trnF (GAA)) are used to explore the systematic relationships of families and subfamilies within the Dicranales. Special emphasis is given to subfamily Dicranoideae of the Dicranaceae, with 17 of the 23 genera represented. 77 taxa are sequenced for trnL - trnF and 69 for rps4, 1247 characters were aligned in the final matrix, of which 1000 characters were used for the analyses. The combined data set was analyzed using maximum parsimony (MP) and maximum likelihood (ML) to examine the generic and familial relationships within the order. Bootstrap values and decay indices show that our data support the following relationships within the Dicranales: 1) the Dicranaceae are polyphyletic, 2) the subfamilies Paraleucobryoideae and Dicranoideae are polyphyletic, 3) the Rhabdoweisiaceae (cf Vitt 1984) are expanded to include members of the Dicranaceae, 4) the subfamily Campylopodioideae has a firm sister relationship to the Leucobryaceae, 5) the Dicranelloideae are excluded from the Dicranaceae sensu stricto, 6) the Dicnemonaceae form a monophyletic clade, including Mesotus (subfamily Mesotoideae, cf Allen 1987) that are nested within the Dicranaceae, and 7) the Ditrichaceae are polyphyletic. The cpDNA data strongly suggest the need for a reevaluation and circumscription of the Dicranaceae. Within the Dicranaceae sensu stricto there are 4 major clades: 1) Leucoloma - Sclerodontium as the basal clade, 2) Dicranoloma - Braunfelsia - Cryptodicranum - Holodontium, 3) Chorisodontium - Orthodicranum - Paraleucobryum - Dicranum - Eucamptodontopsis -Schliephackea - Holomitrium, and 4) Dicnemon,- Eucamptodon - Mesotus clade. Excluded from the Dicranaceae sensu stricto are Arctoa, Brothera, Campylopus, Cynodontium, Dicranella, Dicranodontium, Dicranoweisia, Hydrodicranum, Kiaeria, Kingiobryum, Oncophorus, Oreas, Symblepharis, and Trichodontium.

Key words: cpDNA, Dicranaceae, Dicranoideae, molecular data, phylogenetics