The author mentions three hybrids of Potamogeton species, found in the province of Friesland during the last few years. Two of them, viz. P. lucens L. X P. praelongus Wulf. (P. X decipiens Nolte ex Koch) and P. natans L. X P. zizii Koch ex Roth ( (P. X crassifolius Fryer) were already known from the Netherlands. The third, P. gramineus L. X P. natans L. (P. X sparganifolius Laest. ex Fries), discovered near Oostermeer, is new for our country.