The Ostropales are compared with the Phacidiales, Clavicipitales, Helotiales, Graphidales, Patellariaceae and Gyalectaceae. A close relationship to the Clavicipitales is questioned; the affinities of the group appear to lie with either the Graphidales or the Patellariaceae. The Thelotremataceae are excluded from the Ostropales on the basis of ascospores with lenticular cell lumina and an inner wall which turns red in iodine solutions