A survey was conducted on 84 pig and cattle farms in Denmark between August and October 1996 and1997. The aim was to describe the activity and relative abundance of parasitoids (Hymenoptera: Pteromalidae and Ichneumonidae) that attack puparia of Musca domestica Linnaeus and Stomoxys calcitrans (Linnaeus). In total, seven pteromalid species were recovered: Spalangia cameroni Perkins, S. nigripes Curtis, S. subpunctata Förster, Muscidifurax raptor Girault & Sanders, Pachycrepoideus vindemiae (Rondani), Urolepis rufipes (Ashmead) and Nasonia vitripennis (Walker), an ichneumonid Phygadeuon fumator Gravenhorst, a diapriid Trichopria sp., and a staphylinid Aleochara sp. This is the first time that U. rufipes has been recorded in Europe. Spalangia cameroni and M. raptor were the most frequently recorded species in all regions of the country, and accounted for the main parasitism of Musca domestica and Stomoxys calcitrans puparia. The overall rate of parasitism per farm was low: 12.9% of the total number of fly puparia collected. Direct ordination, used to assess the habitat distribution of the parasitoids, showed that Muscidifurax raptor mainly seeks fly puparia in outdoor manure heaps and especially in manure from pigs rather than from cattle, whereas Spalangia cameroni mainly seeks fly puparia indoors, irrespective of livestock.