The microphytobenthos is the ecological fraction of small plant organisms found in sediments. Hitherto only a few investigations into the microphytobenthos in the southern Baltic have been carried out. The objective of the present study was to determine the species com-position and relative abundance of epipsammic taxa in the shallow littoral zone in the southern Baltic as well as the seasonal fluctuations at selected stations in the Gulf of Gda?sk. The results indicate that three regions of the Polish coastline can be distinguished with respect to the spe-cies composition of microphytobenthic diatoms. The distribution of diatom species is probably related to the environmental conditions occurring in particular regions of the Polish coastline. The percentage of certain diatom species tends to follow a clear seasonal pattern.