This volume is devoted to Quantum Decoherence with lectures from the Séminaire Poincaré, held in November 2005 at the Institute Henri Poincaré Paris. The goal of this seminar is to provide up-to-date information about general topics of great interest in physics. Both the theoretical and experimental results are covered, with some historical background. Particular care is devoted to the pedagogical nature of the presentation.

Decoherence and the Transition from Quantum to Classical - Revisited.- Monitoring the Decoherence of Mesoscopic Quantum Superpositions in a Cavity.- Approaches to Quantum Error Correction.- Decoherence of a Quantum Bit Circuit.- Roots and Fruits of Decoherence.- Dynamical Consequences of Strong Entanglement.