Abstract: Mites of the Genus Demodex are a group of very small mites, parasitic in human beings, domestic and wild mammals, causing skin diseases.The present paper deals with epidemiological studies of the hair follicle mites, Demodex folliculorum, in connection with infection rate, pathogenicity and transmission.In 1979,1524 human cases were studied, including 10 different age groups, from the youngest 4½ months to the oldest 90 years old.The results are as follows.