This review deals with molecular high-resolution spectroscopy based on the quantum beat phenomenon. Applications of the essentially Doppler-free quantum beat technique are presented with special emphasis on the theoretical description. After an historical introduction and a general discussion of interference experiments, we discuss the expressions to describe the time-resolved fluorescence of a molecule following well defined laser excitation. Our general treatment for the characterization of the excited superposition state enables us to demonstrate the versatility of the method by identifying the excited molecular eigenstates with, for example, Zeeman levels or fine- and hyperfine-structure levels. In addition to the spectroscopic applications of quantum beat experiments in determining molecular structure parameters, we address the applications to molecular dynamics and statistical properties of molecular level structures.