Considering a system of two coupled identical chaotic oscillators, the paper first establishes the conditions of transverse stability for the fully synchronized chaotic state. Periodic orbit threshold theory is applied to determine the bifurcations through which low-periodic orbits embedded in the fully synchronized state lose their transverse stability, and the appearance of globally and locally riddled basins of attraction is discussed, respectively, in terms of the subcritical, supercritical nature of the riddling bifurcations. We show how the introduction of a small parameter mismatch between the interacting chaotic oscillators causes a shift of the synchronization manifold. The presence of a coupling asymmetry is found to lead to further modifications of the destabilization process. Finally, the paper considers the problem of partial synchronization in a system of four coupled Rössler oscillators. © 2003 American Institute of Physics. ͓DOI: 10.1063/1.1496536͔The collective behavior of systems of coupled nonlinear oscillators is of significant interest in many areas of science and technology. It is likely, for instance, that transitions between different states of synchronization among the cells or functional units can play a major role in the regulation of many physiological systems. In the field of macroeconomics, synchronization phenomena may explain how the oscillatory dynamics of individual sectors or industries, rather than being averaged out in the aggregate, can lock together and contribute to the formation of the characteristic business and investment cycles. Particularly interesting is the case where the individual oscillators behave chaotically. In the present paper, we use a system of coupled Rössler oscillators to review some of the basic aspects of the theory of full synchronization for time-continuous chaotic oscillators. At the end of the paper we discuss the so-called cluster formation process by which the fully synchronized chaotic state loses its stability and breaks up into groups of oscillators with different dynamics, but such that the oscillators within a given group maintain synchrony.