The references found in the litterature on mite infested cultures of fungi and the difficulties found to eliminate such infestation are summarized. The characteristics of the mite infested cultures, which permit the suspicion of infestation and even to have the certainly of this by the simple observation of the culture tube are described in detail. The authors study the morphology, evolution and habits of the mites which infested the fungi collection of the Instituto Oswaldo Cruz. Such mites were probably Tyroglyphus longior and Tarsonemus floricolus. The experiments made with some drugs against the mites are described. The AA. recommend the use of kerosene either to kill the mites or to prevent new infestations. Kerosene should be dropped on the culture tubes cotton plugs (4-5 drops) and abundantly applied on supports, tables, cupboards, etc; Petri dishes should be placed on paper filter soaked in kerosene.