  We define and study a family of Markov processes with state space the compact
set of all partitions of N that we call exchangeable fragmentation-coalescence
processes. They can be viewed as a combination of exchangeable fragmentation as
defined by Bertoin and of homogenous coalescence as defined by Pitman and
Schweinsberg or Mohle and Sagitov. We show that they admit a unique invariant
probability measure and we study some properties of their paths and of their
equilibrium measure.
