We propose to obtain deep photometry at 60, 90 and 160 microns
 of a carefully selected sample of K giants with 60 micron excess
 in order to determine the nature of the dust emission found in
 these objects. In particular we wish to investigate the possibility
 that the infrared excess is due to debris dust, left over from
 the process of planet formation, which has been re-activated as
 the star leaves the main sequence and evolves to the Red Giant
 phase. If this interpretation is correct, it would imply that
 stars can retain a cold dust shell throughout their main sequence
 life, and would show that the Vega phenomenon may remain active
 throughout the life of low and intermediate mass main sequence
 stars.
 The proposed observations can only be obtained with ISO, since we
 request observations at wavelengths  and with a sensitivity that
 cannot be achieved with any other instrument available at present
 or in the near future.