Description: This paper is the first fundamental study on Spanish Eomyidae. The flourishing time of this family in Europe was the Late Oligocene and Early Miocene. Four genera are recognized in this time span: Rhodanomys Dep\xc3\xa9ret & Douxami, 1902, Ritteneria Stehlin & Schaub, 1951, Pseudotheridomys Schlosser, 1926, and Ligerimys Stehlin & Schaub,1951. The study is based on more than 8000 dental elements from 32 localities, which are situated in the following basins: Ebro Basin (provinces of La Rioja and Huesca), Almaz\xc3\xa1n Basin (province of Zaragoza), Calatayud-Teruel Basin (provinces of Zaragoza and Teruel), Loranca Basin (province of Cuenca), and the Bu\xc3\xb1ol Basin (province of Valencia). The following, anteriorly described species are recognized: Rhodanomys transiens Hugueney, 1969, Rh. schlosseri Dep\xc3\xa9ret & Douxami, 1902; Ritteneria manca Stehlin & Schaub, 1951; Pseudotheridomys schaubi Lavocat, 1951, P. parvulus (Schlosser, 1884), P. fejfari Alvarez & Daams, 1987; Ligerimys antiquus Fahlbusch, 1970, L. florancei Stehlin & Schaub, 1951, L. ellipticus Daams, 1976. Seven new species are described: Rhodanomys oscensis sp. nov.; Ritteneria molinae sp. nov.; Pseudotheridomys lacombai sp. nov.; Ligerimys freudenthali sp. nov., L. fahlbuschi sp. nov., L. magnus sp. nov., L. palomae sp. nov. The evolutionary lineage of Rhodanomys transiens - Rhodanomys schlosseri - Rhodanomys oscensis - Ritteneria molinae - Ritteneria manca is characterized by a simplification of the dental pattern and a reduction of size. The biochronological value of this lineage for the Late Oligocene and Early Miocene is confirmed, and a subdivision of this time interval is made on the basis of the various evolutionary stages. Zone W is characterized by Rhodanomys transiens, zone X by Rhodanomys schlosseri and Rhodanomys oscensis, zone Yl by Ritteneria molinae, and zone Y2 by Ritteneria manca. Fahlbusch (1970) proposed the following phylogenetic model for the Pseudotheridomys - Ligerimys group: Pseudotheridomys parvulus - Pseudotheridomys-Ligerimys transitional assemblages - Ligerimys antiquus - Ligerimys florancei. We think, on the contrary, that two lineages are present in the German material. On the one hand there is a lineage composed of P. parvulus - L. antiquus - L. florancei, characterized by a simplification of the dental pattern and size increase. On the other hand, parallel to this lineage, P. parvulus continues without any apparent changes during the Early Miocene. For that matter P. parvulus is is not considered to be a good biochronological marker for MN zone 2, as it has been found in localities as high as zone MN 4 (Alvarez, Daams & van der Meulen, 1987). In Spain we propose the lineage Pseudotheridomys schaubi - P. parvulus - P. lacombai - Ligerimys antiquus - L. palomae, characterized also by a simplification of the dental pattern, and - contrary to the German situation - by a size decrease. Concurrently, during the early Miocene there is a second lineage, represented by Pseudotheridomys fejfari, characterized by a stable morphology and size increase. Considerable fluctuations are observed in the relative frequency of Eomyidae during the Late Oligoc\xc3\xa8ne and the Early Miocene. These fluctuations are attributed to ecological changes. A high frequency of Ligerimys appears to indicate a relatively humid environment. Se ha realizado por primera vez en Espana una revision de la fam\xc3\xadlia Eomyidae, abord\xc3\xa1ndose el est\xc3\xbadio de los representantes espanoles en el per\xc3\xadodo de mayor abund\xc3\xa2ncia e import\xc3\xa2ncia de la fam\xc3\xadlia en Europa (Oligoceno superior - Mioceno inferior). Cuatro g\xc3\xa9neros est\xc3\xa1n representados para este intervalo: Rhodanomys Dep\xc3\xa9ret & Douxami, 1902, Ritteneria Stehlin & Schaub, 1951, Pseudotheridomys Schlosser, 1926, and Ligerimys Stehlin & Schaub, 1951. Despues dei est\xc3\xbadio sistem\xc3\xa1tico dei material de 32 localidades, que han proporcionado m\xc3\xa1s de 8.000 piezas dentarias, se han determinado las siguientes esp\xc3\xa9cies: Rhodanomys transiens Hugueney, 1969, Rh. schlosseri Dep\xc3\xa9ret & Douxami, 1902, Rh. oscensis sp. nov.; Ritteneria molinae sp. nov., R. manca Stehlin & Schaub, 1951; Pseudotheridomys schaubi Lavocat, 1951, P. parvulus (Schlosser, 1884), P. lacombai sp. nov., P. fejfari Alvarez & Daams, 1987; Ligerimys antiquus Fahlbusch, 1970, L. freudenthali sp. nov., L. fahlbuschi sp. nov., L. magnus sp. nov., L. palomae sp. nov., L. florancei Stehlin & Schaub, 1951, L. ellipticus Daams, 1976. En determinados casos se han establecido las hipot\xc3\xa9ticas relaciones filogen\xc3\xa9ticas entre los distintos taxones diferenciados. Tambien se ha podido constatar el valor biocronol\xc3\xb3gico de la l\xc3\xadnea Rhodanomys - Ritteneria y se han precisado, para Espana, los rangos y distribuciones estratigr\xc3\xa1ficos de las esp\xc3\xa9cies estudiadas.