Biological effects as result of acute oil spill pollution may be considered as a product of: the existing biophysical conditions; occurrence and appearance of organisms in time and space; the fate of the oil in time and space; the vulnerability of the various organisms for oil and oil derivatives in a three-dimensional perspective. In general, it seems as every individual oil spill has its own nature and dynamics, inter alia because the physical, chemical and biological conditions never are the same. This means that the properties of the recipients often are more important than the amount of oil that is spilled. This may be exemplified by two oil spills in recent time. Exxon Valdez (1989), where 35000 ton oil were released in a partly closed sea area, caused considerable effects. From Braer (1993) the double amount of oil was spilled, but in an open sea area and at a time where the presence of dense concentrations of environmental components was limited, and the physical conditions favorable with respect to evaporation and dilution. Preliminary results show that the environmental effects were very limited. 311 refs., 32 figs., 10 tabs.