This account of the taxonomic composition of phytoplankton (mainly microphytoplankton) in the offshore south-eastern Adriatic is a contribution to a check-list of Adriatic phytoplankton, which has not been prepared to date. The investigated area is influenced by warm, highly saline and extremely oligotrophic waters of the north-westerly, inflowing current from the eastern Mediterranean (Ionian Sea). Samples were collected by Niskin samplers and plankton net in the 0¿100 m layer, in April, June and September 1993, and in February 1994. Seven additional cruises in 1979/80 and six cruises in the period from 1981 to 1990 gave data on rare taxa found in net samples only. Two hundred twenty nine taxa have been determined by light microscopy (2 chrysophytes, 12 prymnesiophytes, 95 diatoms, 119 dinoflagellates and 1 prasinophyte).