The paper is an annotated check list of the Decapoda Brachyura hitherto found in the Tyrrhenian Sea, off Monte Argentario at the southern end of the Tuscan Archipelago (Italy). The data were collected in the period 1998-2002 in the framework of a long-term programme to compile a checklist of all decapod taxa. Samples were collected on different substrates, at different depths (0-300 m) and with different collecting methods. Some of the species found are of biogeographical or ecological interest. These include Maja goltziana Oliveira, 1888, Paractea monodi Guinot, 1969, and Paragalene longicrura (Nardo, 1869). Moreover, the record of a specimen of Calappa sp. is discussed. [ABSTRACT FROM AUTHOR]