The nomenclature of the perfect and imperfect stages of Mycosphaerella brassicicola (Duby) Lind. and Leptosphaeria maculans (Desm.) Ces. & De Not. is discussed. The imperfect stages of these two parasites of Brassica spp. are often confused. Mycosphaerella brassicicola has a spermagonial stage with the characters of the form-genus Asteromella Pass. & Thüm. In phytopathological literature it is incorrectly known as a Phyllosticta species: P. brassicicola McAlp. A new combination for this stage is proposed: Asteromella brassicae (Chev.) Boerema & van Kesteren. The pycnidial stage of L. maculans is known in phytopathological literature as Phoma lingam (Tode ex Fr.) Desm. Its characters, however, are quite different from those of the type-species of the form-genus Phoma Sacc. As it agrees with the type-species of the form-genus Plenodomus Preuss, it is concluded that the correct name is Plenodomus lingam (Tode ex Fr.) Höhn.