The phytoplankton diversity was generally low in the Skagerrak and Kattegat areas. Small species like Cryptomonads and Chrysochromulina spp. dominated the samples. A few diatoms were found with moderate cell numbers at Släggö (Skagerrak coast) and in the Kattegat. The dinoflagellate Prorocentrum minimum and the filamentous cyanobacterium Anabaena spp. were found with moderate cell numbers at the Kattegat phytoplankton stations. The integrated (0-20 m) chlorophyll a concentrations were within average for this month in the Skagerrak area. In the Kattegat the integrated values were on the limit to being below average. The phytoplankton situation was very similar within the Baltic stations. Two or three of the most common filamentous cyanobacteria were observed in various amounts at all stations as well as high numbers of small flagellated species. The potentially toxic cyanobacterium Nodularia spumigena was common at BY5, BCSIII-10 and BY15, in the same areas as surface aggregations of cyanobacteria were observed. The integrated chlorophyll a concentrations were within average for this month at all Baltic stations.