This explosion of information about sea ice has fascinated scientists for some 20 years we are now at a point of transition in sea ice studies we are concerned less about ice itself and more about its role in the climate system this change in emphasis has been the prime stimulus for this book. In this paper some of the recent results on the microwave remote sensing of sea ice will be reviewed emphasis is placed particularly on results obtained since the comprehensive articles of campbell et al 1978 and gloersen et al 1978 unfortunately seasat failed prior to the planned surface and aircraft underflight experiments so that reference is here often made to aircraft work in order . During the aidjex main experiment april 1975 through may 1976 a comprehensive microwave sensing program was performed on the sea ice of the beaufort sea surface and aircraft measurements were obtained during all seasons using a wide variety of active and passive microwave sensors the surface program obtained passive microwave measurements of various ice types using four antennas mounted on a tracked vehicle in three test regions each with an area of approximately 15 x 10. Microwave remote sensing of sea ice carsey frank d abstract human activities in the polar regions have undergone incredible changes in this century among these changes is the revolution that satellites have brought about in obtaining information concerning polar geophysical processes satellites have flown for about three decades and the polar regions have been the subject of their