INTRODUCTION In recent years there has been a growing awareness and concern about the potential effects of offshore industrial activities on marine mammals. In many cases these concerns have focused on the oil and gas industry in North American waters@ particularly in arctic and subarctic areas. However@ industrial activities and other potential disturbances have occurred for many decades in offshore and coastal waters occupied by marine mammals. Aside from offshore petroleum operations@ these activities include a large amount of commercial shipping in progressively larger and faster vessels@ military fleets@ world wars accompanied by large oil spills and explosive anti-submarine warfare@ oil spills from commercial vessels@ large offshore and coastal fishing fleets@ whaling and sealing fleets@ recreational vessels@ coastal developments and ports. Thus@ marine mammals have been exposed to a great many potential disturbances@ especially in non-arctic waters. The objective of this report is to review the available information on the effects of these activities on marine mammals@ with special reference to mammals occupying cold waters. In other words@ what have we learned about the effects of existing activities and are these lessons applicable to arctic areas? A series of recent and ongoing studies have specifically addressed some of the questions relating to the potential effects of offshore oil and gas activities in arctic waters. Available information from these studies is also reviewed and assessed.