Abstract: After an oil spill on the ocean surface the spilled petroleum can lose up to 40% of its initial weight due to evaporation.Petroleum is a complex mixture of different components and the evaporation of petroleum is very different from that of water. Evaporation of water if regulated by a air boundary layer above the surface. Petroleum evaporation is not regulated in the same way and it is mostly uneffected by wind or slik area. Despite of the difference in the regulaton mechanism of petroleum and water the initial equation for the early work on petroleum evaporation is the euation for water evaporation: E≥KCTuS. Two different models are observed: semi-analythical and fugacity model. In the semi-analythical model the spill is divided into N number of smaller parts wich have different propeties. For a give time period the evaporation of these part is calculated, evaporated or sunk components are removed from further calcualtions. the remaining components are the unified to a sema layer thicknes and the calculation is then repeated for a new time period. The fugacity model divides the spill area into two components: water and sediment. Water is further divided int suspended solids and biota. Sediment is divided into pore water and solid matter. This model predicts the grow of the water part due to the spreading of the oil spill. It also takes into consideration the sea curents and chemical degradation of petroleum. With the increase of petroleum transportation and growing risk of accidents new computer programs for predicting the fate of oil spills and their weathering are developed.