The molecular mobility of amorphous anhydrous trehalose (C12H22O11) was investigated by means of temperature-modulated differential scanning calorimetry (TMDSC) and dielectric analysis (DEA). TMDSC was used to perform a specific heat spectroscopy, which appeared essential, as dielectric measurements above T-g were hampered by dc conductivity. TMDSC and DEA are useful complementary techniques for the study of the molecular mobility of this important bioprotecting agent. The study of the primary relaxation of trehalose, above the glass transition temperature, yielded the determination of the fragility index m and the stretching exponent beta. The correlation between m and beta was also discussed. Dielectric studies of the sub-T-g domain highlighted two distinct secondary relaxation processes, whose dynamical features were evaluated.