The genus Prolistrophorus Fain, 1970 (Acari, Listrophoridae) now comprises, including the new taxa described herein, 26 species grouped in three subgenera. These species live attached permanently to the hairs of their hosts. The whole group is confined to North and South American rodents or South American marsupials. The genus Prolistrophorus is redefined and new characters are provided for the definition of the three subgenera: Prolistrophorus s.st., Aprolistrophorus Fain, 1980 and Beprolistrophorus Fain, 1980. Complete descriptions with figures are given for the first time for eight insufficiently known species: P. grassii (Radford, 1954), P. pernamboucensis Fain, 1973, P. scotinomys Fain & Lukoschus, 1982, P. postscutatus Fain & Lukoschus, 1982, P. reithrodontomys Fain & Lukoschus, 1982, P. lestoros Fain & Lukoschus, 1982, P. cuzcoensis Fain & Lukoschus, 1982 and P. akodon, Fain & Lukoschus, 1982. Four new species are described and depicted: P. primitivus, P. curvistriatus, P. monilistriatus and P. bidentatus. Keys to females and males are provided for all the known species of the genus. The origin and the evolution of this genus are discussed. ac]19830401