Ectoparasitic mites on Brazilian non-poisonous snakes, collected from March 1976 to December 1979, are herein reported. A systematic study of the Ixodorhynchidae, which include exclusively parasites of snakes is given, including all immature forms. Two new genera are described: Ophiogongylus gen.n. with two species: Ophiogongylus rotundus sp.n. and Ophiogongylus breviscutum sp.n. and Chironobius gen.n. with two species: Chironobius alvus sp.n. and Chironobius nordestinus sp.n. Ixobioides brachispinosus sp.n. and the male of Ixobioides fonsecae (Fain) are also described. Immature forms, hosts relations and geographical distribution are given for the species.