A recent CSO submillimeter continuum survey of the nuclear disk
 revealed a number of unique compact dust condensations forming an
 elongated ridge connected to the Galactic center radio arc. No compact
 FIR sources or HII regions associated with these dust condensations
 are found in the existing surveys. These massive GMC cores thus appear
 DISTINCTLY DIFFERENT FROM PREVIOUSLY STUDIED GALACTIC CENTER SOURCES.

 The detection of MASSIVE AND COLD GMC CORES in the nuclear disk,
 apparently WITHOUT ONGOING HIGH-MASS STAR FORMATION, would be of great
 importance, allowing a new assessment of the contributions of various
 dynamical effects that have been invoked to explain the low rate of
 high-mass star formation in the central region. To gain definitive
 information on current star-formation in the Galactic center dust
 ridge, we initiated a multi-wavelength observing campaign to search
 for signposts of young high-mass stars, such as H2O masers and
 ultracompact HII regions. Preliminary results indicate that both,
 masers and compact continuum sources, are very rare in the dust ridge.

 We propose ISOPHOT 60 and 105 micron observations to address two of
 the most important outstanding questions in this matter. First, these
 observations will allow a sensitive search for compact luminous FIR
 SOURCES EMBEDDED IN THE DUST CORES that is three orders of magnitude
 more sensitive than earlier surveys. Second, they will yield estimates
 of the dust temperature throughout the dust ridge and thus allow
 meaningful mass derivations. Existing multi-wavelength submillimeter
 observations predict observable 100 micron emission from extended
 portions of the ridge for all plausible values of the dust temperature
 and grain emissivity. With the KAO decommissioning planned for
 1995, ISO is the only instrument capable of performing these
 observations within the next 6-7 years.