Mycosphaerella punctiformis, the type species of the genus Mycosphaerella, is epitypified by material collected on Quercus robur in The Netherlands. The teleomorph is described in planta, and the Ramularia anamorph, for which the new name R. endophylla is proposed, and the Asteromella spermatial state are characterized in vitro. Sequence data of the nuclear ribosomal DNA are presented and analyzed together with other Mycosphaerella spp. with Ramularia and several other anamorphs. Several strains originating from Quercus, Acer and Tilia showed diverging ITS sequences, indicating that the M. punctiformis complex may comprise more than a single phylogenetic species, but this could not be confirmed by the analysis of our dataset. An endophytic phase is established for the first time in the life-cycle of M. punctiformis, as the species was repeatedly isolated from surface sterilized green healthy leaves of Quercus robur in summer at the epitype locality.