This article covers the rotifer data from a 1987/1988 survey of one hundred Spanish reservoirs. From each species brief information is given, focused mainly on ecology, morphology, zoogeography and distribution both in Spain and within reservoirs. New autoecological information on each species is also established giving conductivity ranges, alkalinity, pH and temperature for each. Original drawings and photographs obtained on both optical and electronic microscopy are shown of the majority of the species found.In total one hundred and ten taxa were identified, belonging to 101 species, representing 20 families: Epiphanidae (1): Brachionidae ( 23); Euchlanidae (1); Mytilinidae (1 ): Trichotriidae (3): Colurellidae (8); Lecanidae ( 1 5 ) ; Proalidae (2); Lindiidae (1); Notommatidae ( 5 ) ; Trichocercidae (7); Gastropodidae ( 5 ) ; Synchaetidae (1 1); Asplanchnidae (3); Testudinellidae (3); Conochiliidae (5): Hexarthridae (2); Filiniidae (3); Collothecidae (2); Philodinidae (Bdelloidea) (I).Thirteen species were new records for the Iberian rotifer fauna: