In the house dust there are different species of mites, which have medical importance because they are related to allergic asthma, rhinitis and/or dermatitis. Between april-august 1989 and march-june 1990, 100 samples of house dust collected in the city of Valdivia, Chile were analyzed. By using special techniques the samples were examined and classified. In the present research 70 samples of dust were positive, which showed one or more species of mites. Thirteen species and one genus were classified. The average quantity of house dust examined by sample was 0.69 g and a total of 701 mites were isolated, being identified 691 of them: Glycyphagus destructor (23.4%), G. domesticus (22.7%), Blomia tjibodas (19.2%), Cheyletus eruditus (6.5%) and Chortoglyphus arcuatus (12.0%), were the most frequent species found. In 74.2% of the positive samples two or more species of mites were observed, being the most common the association of two species, with the combinations: G. destructor-G. domesticus; G. domesticus-Tyrophagus putrescentiae; G. destructor-Ch. eruditus.