Between March 2004 and July 2005, the mites associated with whole wheat, flour and sweepings (residue from, for example, the floor, equipment and the outside of sacks) in 16 flour mills in the Karaj region of the Tehran Province of Iran were surveyed. Sampling was carried out in the spring (March, April and May), summer (June, July and August) and early autumn (September and October). Mites were found in five of the mills. Nine species were recorded, namely, Acarus farris Oudemans, A. siro Linnaeus, Tyrophagus longior (Gervais), T. putrescentiae (Schrank), Lepidoglyphus destructor (Schrank), Androlaelaps casalis (Berlese), Rhysotritia ardua (C. L. Koch), Acaropsellina sollers (Kuzin) and Cheyletus carnifex Zachvatkin. Mites were found in 94% of the sweeping samples, 68.57% of the flour samples and 53.3% of the whole wheat samples.