A total of 38 219 specimens representing 63 species of marine isopods (Crustacea) from deep and shallow Arctic waters were studied in a search for epizoic foraminifers (Protozoa). Foraminifers occurred on 21 species, and their frequency was generally low. A total of 290 foraminifer individuals were found, of which 289 belonged to Cibicides wuellerstorfi, C. refulgens and Cibicides spp. (juveniles) (Cibicidae), while only a single individual belonged to Cornuspira sp. (Cornuspiridae). The foraminifers were most frequent on species of the families Munnidae, Ischnomesidae (suborder Asellota) and on Gnathia stygia (suborder Gnathiidea), but were totally absent from the asellote families Janiridae, Haploniscidae, Nannoniscidae and from the suborder Epicaridea. The foraminifers were mainly located on the legs (Munna acanthifera), the anterior part of the body (Haplomesus quadrispinosus, heteromesus frigidus), or on the head (G. stygia adults). The epizoic foraminifers occur mainly on epibenthic isopods, which do not or only rarely clean themselves. The foraminifers are known to prefer elevated substrata, and in this the habitat of the isopods and the foraminifers coincide. The size of individual isopods was not related to the presence or absence of foraminifers.