A multi-wavelength ISOPHOT study is proposed to measure
 the IR energy distributions of a sample of protostar
 candidates.  During a recent ground-based survey at the
 IRAM 30m and at SEST, we have discovered a number of so
 far unknown sources of strong mm emission, which
 are the coldest and densest dust condensations ever
 found.
 Despite our subsequent submm photometry at the JCMT it
 was not possible to constrain the temperature sufficiently
 well. The proposed ISOPHOT measurements will be combined
 with our existing mm/submm photometry in order to
 determine temperature, luminosity, mass, and evolutionary
 status of these young objects. Microscanning with ISOCAM
 will be performed to reveal possible embedded stellar sources.