6-Propionyl-2-(dimethylamino)naphthalene (PRODAN) has been widely used to probe the internal environment of sol−gel derived glasses. It is generally assumed that the entrapped probe reports primarily on the internal solvent environment, through changes in emission wavelength, lifetime, or anisotropy. However, we show that other effects, such as aggregation of the probe and adsorption of the probe onto the silica surface, can also alter the emission properties of PRODAN, providing further information on the evolution of sol−gel derived glasses. Both the steady-state and time-resolved fluorescence properties of PRODAN were examined when the probe was entrapped in tetraethyl orthosilicate (TEOS) derived glasses. The glasses were prepared using a two-step method that is commonly used for protein entrapment, and aged either in air without washing (dry-aged), in air after a washing step (washed), or in buffer (wet-aged). For all aging methods, the changes in the emission properties of the probe were consistent with at least three discrete microenvironments, reflecting free monomers, free aggregates, and adsorbed species (monomers and/or aggregates), the proportion of which changed as a function of drying time and conditions. The monomeric form of the probe underwent a polarity-sensitive emission shift that reflected changes in the internal solvent composition. However, the aggregates/adsorbates contributed unique features to both the steady-state and time-resolved emission properties of PRODAN that gave insights into changes in the solubility of the probe, consistent with loss of internal solvent as aging of the glass proceeded. This study clearly shows that significant new information can be obtained from studies of PRODAN emission, and demonstrates that time-resolved fluorescence measurements are critical to properly elucidate the environment(s) present within the sol−gel derived materials.