We report the identification, from a 1.2 mm dust continuum emission survey toward massive star-forming regions, of four strong 1.2 mm sources without counterparts at mid-infrared (Midcourse Space Experiment [MSX]) and far-infrared (IRAS) wavelengths. They have radii in the range 0.2-0.3 pc, dust temperatures ≤17 K, masses in the range 4 × 102-2 × 103 M☉, and densities of ~2 × 105 cm-3. We suggest that these objects are massive and dense cold cores that will eventually collapse to form high-mass stars.