Seasonal changes in the composition, abundance and biomass of zooplankton in the seas of the Mediterranean basin (the Mediterranean, Black and Azov seas) have been reviewed using our own data and data from the literature. In the deep-water central regions of the seas, the seasonal cycle of zooplankton abundance is characterised by one maximum occuring in spring or summer. in the coastal regions, two to three peaks (spring, summer and autumn) exist for the zooplankton abundance. The amplitude of seasonal fluctuations in abundance for the coastal zone as a rule is much wider than for the deep-water regions. In both coastal and central deep-water regions, the amplitude of seasonal fluctuations increases from the Mediterranean to the Black and Azov seas, as well as from south to north in each sea. This corresponds to seasonal changes in the amplitude of water temperature and the abundance of phytoplankton as the basic factors influencing zooplankton abundance. The dominant role in defining seasonal changes in total zooplankton abundance is played by the main group - copepods, which in some years form up to 90% of zooplankton numbers and biomass. During the warm period of a year, cladocerans may replace copepods.