Eight different passive microwave sea ice algorithms were implemented and compared to each other and showed discrepancies in retrieval of the sea ice concentrations in the Arctic, leading to uncertainty in estimation of the total amount of the sea ice. Therefore the algorithms need to be validated making use of other than passive microwave data. Synthetic aperture radar (SAR) was chosen as the main tool for such a validation due to its high resolution, wide swath and ability to measure independently on weather or daytime. Envisat ASAR data from European Space Agency (ESA) have been used. So far only the sea ice edge position obtained by the passive microwave algorithms was compared to SAR. The comparison showed that all the algorithms give the sea ice edge position very closely to one retrieved from SAR with the error of one pixel size of passive instruments.