The microscopic dynamics of several monomeric and polymeric glass-forming materials has been investigated by time-resolved fluorescence measurements of doped malachite green molecules in a wide temperature region. For monomers, 1-propanol, propylene glycol, and glycerol, and a polymer without side chains, polybutadiene, the temperature dependence of nonradiative decay time of doped malachite green molecules behaves in a similar way through the glass-transition region. Besides a kink around the calorimetric glasstransition temperature T g , another crossover at a critical temperature T c about 30-50 K above T g has been clearly observed. This experimental finding is in agreement with the prediction of the mode-coupling theory that a dynamical transition exists well above T g . On the other hand, for the complex polymers with side chains, poly͑vinyl acetate͒, poly͑methyl acrylate͒, and poly͑ethyl methacrylate͒, the crossover at T g is less pronounced than those for the monomers and the polymer without side chains. Moreover, although we could not distinguish any singularities above T g for these complex polymers, we observed another kink below T g , which may be attributed to the side-chain motions. ͓S0163-1829͑97͒02333-3͔