Interactions between phyto- and zooplankton species have been discussed on the basis of literature data and partially of own, rather general investigations. The ways of taking food by zooplankton was reviewed. The literature data on potential consumers of phytoplankton taxa of a different size is presented in a tabular form. Two aspects of interactions have been analysed: influence of zooplankton on the dynamics and adaptive responses of phytoplankton; phytoplankton as factor stimulating zooplankton development.