A new genus classification of the Thelotremataceae is presented. Myriotrema, Ocellularia and Thelotrema sensu HALE (1980, 1981) were found to be heterogeneously circumscribed and were segregated into more natural units. The following changes are made: Ampliotrema Kalb is validated, and Chapsa Massal., Leptotrema Mont., Leucodecton Massal. and Stegobolus Mont. are resurrected. The genera Acanthotrema A. Frisch, Gyrotrema A. Frisch, Melanotrema A. Frisch and Redingeria A. Frisch are described as new to science. 19 genera are accepted for the family: Acanthotrema, Ampliotrema, Chapsa, Chroodiscus, Diploschistes (not treated), Fibrillithecis, Gyrotrema (part II), Ingvariella (not treated), Leptotrema, Leucodecton, Melanotrema (part II), Myriotrema, Nadvornikia (not treated), Ocellularia, Redingeria (part II), Reimnitzia, Stegobolus (part II), Thelotrema and Topeliopsis. The Thelotrema glaucopallens- and the Ocellularia clandestina -group are of uncertain generic affiliation.