Three populations of common reed (Phragmites australis (Cav) Trin. ex Steud.), growing under differing edaphic conditions in lakes near the town of Koszalin (the Pomerania region in north-western Poland), were studied in respect to frequencies of electrophoretically detected allozymes in two peroxidase loci: a monomeric locus with three alleles and a dimeric locus with two alleles. On the basis of genetic distances, similarity between these populations and levels of variation were assessed both within populations (GST = 0.0376) and between populations (DST = 0.0194). Gene flow between populations was low (Nm = 6.399).