Abstract. Abstract: The present study has conducted a minireview of ecotoxicological studies using ciliated microeucaryotes, presenting a breif history, describing the current scenario and pointing out their methodological approaches gaps. We highlight in a clear and objective way the ecological importance of ciliates for ecosystems, their usefulness and the inherent characteristics that classify them as a good model organism. Finally, we discuss some modern tools that can be added to studies with ciliates in the near future.