Rotifera is a group of pseudocoelomate aquatic invertebrates with great potential as model organisms for ecotoxicology and genotoxicology. This potential is based on their: (a) fast growth and reproduction, (b) ease of culture and maintenance, (c) cyst production, (d) alternation of asexual and sexual generations, among others. While the use of rotifers as models for ecotoxicology is well documented and more species, tests, and information are added every day, the potential use of rotifers for genotoxicology is still very limited. In this chapter the authors attempt to explain the state of the art regarding the use of rotifers as models for both eco- and geno-toxicology. To achieve this, the authors have implemented a complete search in the mainstream scientific literature describing types of studies, perspectives, and use of rotifers in both areas. In the case of genotoxicology an emphasis has been made to incorporate suggestions on the advantages that rotifers represent if used as model organisms for the different techniques and studies instead of the most traditionally used organisms. Among the main topics included in genotoxicity are: (a) aging, (b) horizontal gene transfers and gene conversion induced by chronic exposure, (c) detoxification mechanisms, (d) transgenerational effects, and (e) micro evolution as mechanisms of adaptation to toxic exposure.