Like other meetings in the Royal Society’s programme, this Discussion Meeting is concerned primarily with science: in the present case, the scientific evaluation of the consequences of polluting the marine environment with oil. This has, of course, also formed an important part of the study of oil pollution of the sea undertaken by the Royal Commission on Environmental Pollution (1981), but in its role as an advisory body on pollution matters to government, the Commission’s interest is much wider. Government must be concerned not only with the threat that oil pollution may pose to the marine environment or to human health, as seen by the scientific community, but with many other aspects that affect public perception of the problem and that have a bearing on decisions on the means of dealing with it. Oil spills appear to generate wider concern than do most other forms of pollution, even among people whose interests are not directly affected. The environmental insult of a large spillage of black oil is so apparent that emotions are deeply stirred; these emotions are aroused especially by the distress caused to seabirds. The strength of feeling here reflects not only a civilized revulsion, that animals deserving our protection should be wantonly destroyed, but perhaps also reflects a collective guilt that a substance on which our way of life so much depends should cause such havoc. At any rate, the public’s response to oil spills is a real factor that must be recognized in considering policies for control. Against this, it was important for the Commission to be always aware that its task was to see the threat posed by oil pollution in perspective. It would have failed in its task had it allowed an emotional reaction to the grosser manifestations of oil pollution to persuade it to advocate inadequately considered countermeasures, which might well have been costly and of doubtful effectiveness.