This thesis concerns the effect of marine pollutants on marine mammals, whit special focus given Bergmans studies on the Baltic grey seal. Environmental pollutions have gained increasing attention the last few decades, and the alarming levels of certain pollutant compounds found in the biota caused by the worldwide spread of anthropogenic pollutants like PCBs and DDTs, has led to numerous studies on the subjects. Potential ways in which chemical compounds may manifest themselves include direct mortality, reproductive impairment, and increased susceptibility to disease. It is often assumed that sublethal toxic effects of persistent contaminants will ultimately alter population size. Unfortunately, field studies are hampered by many confounding variables, obscuring the nature of various associations and possible cause- end effect relationships. According to Tannabe (1988) the ocean serves as sink for most pollutants, and due to their lipophilic characteristics, the levels of several pollutants found has stagnated and exposure to these contaminants can be expected in the coming decades.