Altogether 832 mammals representing 16 species were collected from the Chiricahua Mountains in southeastern Arizona and examined for fleas and lice. Sixteen species of Siphonaptera, 2 species of Mal-lophaga and 11 species of Anoplura were collected. The fleas showed more relationship in their distribution to the physical habitat than to the host species. Most of the lice were quite host specific. The size of the louse populations varied widely from host species to host species and on the Merriam''s kangaroo rat between sexes of the host. The sex ratios of the several louse populations varied from 29.0% to 50.8% males. The number of immature lice varied from 0.37 to 6.92 per adult female.