The genus Tricholoma contains several taxonomically difficult groups. During the revision of the genus Tricholoma for the Flora agaricina neerlandica, vol. 4 (Bas et al., in press) some of these groups have been tackled. Detailed studies are presented of sect. Lasciva and sect. Atrosquamosa subsect. Terrea with keys, descriptions, and comments. Where possible neotypes or epitypes have been designated. In addition two new varieties are described in other sections, viz. Tricholoma psammopus var. macrosporum and T. equestre var. populinum. Notes are given on some nomenclatural problems within the genus Tricholoma.