Despite the economic importance of eriophyoid mites as agricultural pests, especially of cereal crops, knowledge of the eriophyoid fauna in Turkey remains incomplete. This article presents the results of a 3-year study on grass-infesting eriophyoid mites in Turkey. The aim of this study was to collect and identify eriophyoid species infesting wild and cultivated grasses and to estimate the degree of overall mite infestation on grasses. The study involved both qualitative samples (to record the presence or absence of mites) and quantitative samples (to investigate the parameters of mite infestation: viz. prevalence, intensity and density). Seven eriophyoid species - Aceria tosichella (Keifer, 1969), Abacarus hystrix (Nalepa, 1896), Abacarus lolii Skoracka, 2009, Aculodes holcusi Skoracka, 2004, Aculodes dubius (Nalepa, 1891), Abacarus longilobus Skoracka, 2002, Aculodes sp. nov. - were collected from grasses in the course of this study. Quantitative data were available for the first four of these species, and parameters of infestation differed greatly among the hosts. Aceria tosichella was the species infesting the largest number of grass species, and A. hystrix was the species with the highest values of prevalence and density on wheat. New host species for A. tosichella were reported, including Dactylis glomerata, Bromus sclerophyllus, Eremopyrum orientale, Lolium temulentum and Poa bulbosa, all for the first time in Turkey.