Interactions between marine mammals and fisheries were monitored along the southwestern Atlantic coast of Argentina from Bahia Samborombon (Buenos Aires Province) to Tierra del Fuego Island. A variety of fisheries with several types of gear are used and in some fisheries there are incidental catches of small cetaceans. Different cetacean species are taken depending on area, gear and target fish species involved. However, throughout the region, information is scarce and good estimates of mortality and the stock identity and abundance of the affected marine mammal species are required. In Buenos Aires Province, the franciscana, Pontoporia blainvillei, is the species most frequently caught in shark and croaker gillnet fisheries. In some places in this province, such as Necochea (the best studied area of Argentina), gillnets also catch Burmeister’s porpoises (Phocoena spinipinnis) and purse seines catch dusky, common, and bottlenose dolphins (Lagenorhynchus obscurus, Delphinus delphis and Tursiops truncatus). Passive fishing gear is not used in the area between San Matias Gulf and San Jorge Gulf, but bottom and mid-water trawls, mainly for shrimp and hake, catch dusky dolphins and to a lesser extent common dolphins, Commerson’s dolphins (Cephalorhynchus commersonii) and spectacled porpoises (Australophocoena dioptrica). Although the dolphin mortality per fishing vessel and per month seem to be low, the high level of fishing effort may result in a high absolute number of dolphins killed. In southern Patagonia (Santa Cruz Province, south of Puerto Deseado) gillnets are used for robalos (Eleginops madovinus); Peale’s dolphin (Lagenorhynchus australis), Commerson’s dolphins and spectacled porpoise are caught incidentally. At Tierra del Fuego Island, gillnets are used for robalo, hake and silverside on the northeast coast and take Peale’s and Commerson’s dolphins and spectacled and Burmeister’s porpoises. The use of marine mammals as bait for fishing centollas seems to have decreased recently in the Argentinean section of the Beagle Channel, but information on mortality rates is far from complete. In some localities the southern sea lion (Otaria flavescens) has been reported to damage catch and nets and is occasionally entangled. When considering management and conservation strategies, the economy and market conditions are important variables in less developed countries and should be studied along with biological parameters.