The harbour porpoise is the only cetacean common to Swedish waters. This paper reviews data on harbour porpoise bycatches in the Swedish Skagerrak, Kattegat and Baltic Seas between 1973 and 1993. Bycatches in various fisheries are the major threat to harbour porpoises in Swedish waters. Gillnet fisheries are responsible for more than 80% of all incidental takes. Although bycatches occur year round in all areas, 51% were collected during three months; March, April and May. Bycatches occur in water depths between 0 and 100m, suggesting that depth restrictions for fisheries are not likely to reduce catches. In the Skagerrak Sea, 47.5% of the bycatches were taken in gillnets set for spiny dog fish in water depths between 40-80m; in the Kattegat Sea 72% were taken in gillnets set for cod in depths between 20-60m and in the Baltic Sea, 53.8% of the bycatches were taken in surface driftnets for salmon. It is not possible to quantify the threat bycatches represent to harbour porpoises in Swedish waters in the absence of reliable estimates of bycatches or abundance and uncertainty over stock identity. However, the existence of bycatches is a serious cause for concern and immediate action is needed.