In this paper the potencial of flow cytometry as applied to the aquatic life sciences is discussed. The use of flow cytometry for studying the ecotoxicology of phytoplankton was introduced. On the other hand, the new flow cytometer EUROPA was presented . This is a multilaser machine which has been specially designed to have a high volumetric throughput and wide dynamic range: purpose-built modules allow single cell diffractometry and video imaging in flow which help greatly with morphological analysis and taxonomic identification.