In January and September of 1989 and March 1990 blooms of Oscillatoria rubescens, Oscillatoria tenuis and Oscillatoria mougetii were found in Lake Simbirizzi and Lake Flumendosa in Sardinia, and in Lake San Puoto in the Lazio region of Italy. By using different extraction methods and HPLC analysis, two microcystin-like toxins (RR-like and YR-like), similar to some of the toxic compounds produced by the Cyanophycea Microcystis aeruginosa, were detected in these blooms