The northern part of the BalticSea becomes ice covered each year and icebreakers operate in the area to assist and route the ship traffic. The Baltic Experiment for ERS-1 (BEERS) is a research programme to introduce and evaluate the use of satellite synthetic-aperture radar (SAR) images in support of winter marine traffic. Four field experiments and one operational demonstration have successfully been carried out during 1992-1994. In this chapter, we describe the Swedish BEERS experiments and summarise the main results. The present limitations for operational use of the SAR images are due to spatial coverage and temporal sampling restrictions. Daily coverage of the entire Baltic Sea area at a resolution of 100-200 m is recommended for a future operational system. Measurement results show that the SAR images mainly respond to roughness variations of the ice surface. The SAR images thus provide unique information on the ice conditions independent of daylight, clouds and fog. Models of the interaction between the radar wave and the ice surface have been used for image inversion to retrieve surface roughness. Preliminary analysis also show good correlation with ice resistance measured from ship performance data. Image interpretation is not affected by air temperature or precipitation during cold conditions, but becomes difficult as the air temperature rises above 0°C when wet snow masks the ice surface. Discrimination of open water leads and sea ice is difficult based on image tone and texture alone, but is a minor problem for a trained operator. SAR interferometry is a new technique which shows good potential for measuring small-scale motion (cm) over large areas.