The first synoptic basin-wide oceanographic survey in the Eastern Mediterranean Sea was carried out in October-November 1991 within the framework of the international programme POEM-BC (Physical Oceanography of the Eastern Mediterranean - Biology, Chemistry). Mesozooplankton samples were collected at 32 stations in the Sicily Channel, Ionian Sea, Cretan Sea, Cretan Passage, Rhodes area and central Levantine Sea. Vertical hauls were taken from four discrete depth layers in the upper 300 m water column. The gross features of the mesozooplankton communities, at the phyla, class or order level, are described. Depth-integrated abundances showed high homogeneity within each region, with the highest and lowest values recorded in the Sicily Channel (mean: 200 ind. m(-3)) and in the Cretan Sea (mean: 45 ind. m(-3)), respectively. Strong vertical gradients in zooplankton distribution were evident at all stations, the 0-50 m layer being the richest in numbers, whereas numbers sharply decreased at 100 m depth. Copepod relative abundances accounted for approximately 80% of the total zooplankton numbers, while ostracods (6.4%), chaetognaths (4.2%), appendicularians (4%) and pteropods (1.7%) followed in rank order. It seems that the zooplankton distribution is not always influenced by local meso-scale dynamics, but only when the physical forcing is strong and persistent over time, as in the Rhodes gyre area.