The harbour porpoise (Phocoena phocoena) is the only cetacean incidentally caught in significant numbers by the Danish fishing fleet and there is some concern that the populations in Danish waters may be in decline. The main catches are in the extensive fleet of vessels fishing dermersal gillnets. Recently, this bycatch has been quantified by a rough estimate of up to 7,000 bycaught harbour porpoises and public and political awareness of the issue is increasing. This paper reviews the Danish passive gear fishery and the level of the bycatch of harbour porpoises. Methods with potential for reducing this bycatch are briefly discussed.