The monthly abundance, biomass and taxonomic composition of zooplankton of Sinop Inner Harbor (the southern Black Sea) were determined during 2002-2004. Samplings of zooplankton were carried out vertically at monthly intervals using a standard type plankton net (210 mm mesh size and 50 cm diameter mouth opening). In the present study, a total of 25 zooplankton taxa were identified. The highest abundance values of mesozooplankton were encountered in February 2003 (193,500 ind. m-2), particularly due to Pseudocalanus elongatus (83,300 ind. m-2) individuals. The mesozooplankton biomass, on the other hand, was the highest in August 2004 (4350 mg. m-2), due to Acartia (Acartiura) clausi (1820 mg. m-2). The heterotrophic dinoflagellate Noctiluca scintillans, was a major component of plankton samples in Sinop region, presenting its highest values in May 2004. Total annual distribution in mesozooplankton abundance and biomass values showed no significant differences (P > 0.05) among the three years. Detailed results which have particular importance for long-term assessment of the state of the ecosystem and for modeling studies show that during 2002-2004 mesozooplankton levels off Sinop were rather low compared data from other coastal areas.