Abstract. The synchronization of periodic and chaotic oscillations in finite-dimensional dynamical systems is considered on the basis of the classical theory of oscillations. The concepts of the classical theory are applied to nonlinear systems in which oscillations are induced by external noise. The effects of stochastic synchronization and coherence resonance are investigated. It is established that the stochastic synchronization is associated with the locking of the instantaneous phase of chaotic or stochastic oscillations accompanied by the locking of the mean frequency. The results are illustrated by numerical simulation and by radiophysical and medico-biological experiments.