On 11 species of small mammals collected in the parks and ruderal areas of Moscow in 1964-1991, 35 species of mites were revealed. Among them 23 species were parasitic. Laelaps hilaris, Haemogamasus nidi, and Androlaelaps glasgowi were predominant. The mite species diversity on small mammals in Moscow is similar to that in natural environments. The epidemiological and epizootiological significance of revealed species of mites is discussed. The rat mite Ornithonyssus bacoti has the major medical importance as the pathogen of the rat mite dermatitis in Moscow and as a vector of transmissive diseases. According to literature and the data obtained the favorable conditions for maintenance of transmissive diseases reservoirs exist permanently in Moscow.