An oil spill model, which accounts for the sinking effect, was developed. The main processes that affect the fate of oil released into the environment, for the first days of the spill, are included. These are evaporation, spreading, dispersion, emulsification and sinking. Special consideration is given to the process of sinking of oil, and the conditions at which this to occurs are described. Also, the basic equations for determining the breaking of the spill in fragments, the size of this fragments, the overwash depth, the maximum sinking depth and the distribution of oil in the water column are given. The model is applied t.o two hypothetical spills of 1000 m3 in stratified waters. The two spills differ in the density of the oil, 900 and 990 Kg/m3. In the first case the oil disappears from the surface after seven days at sea, mostly from evaporation and dispersion, while in the second case, because the high density of the oil, the spill sinks completely after 18 hours at sea.