We study the cosmological scenario arising from the dynamics of a generalized Chaplygin gas .
The equation of state of the system is given in terms of the energy density , \rho , and pressure , p , by the relationship p = - A / \rho ^ { \alpha } , where A is a positive constant and 0 < \alpha \leq 1 .
The conditions under which homogeneity arises are discussed and it is shown that this equation of state describes a universe evolving from a phase dominated by non-relativistic matter to a phase dominated by a cosmological constant via an intermediate period where the effective equation of state is p = \alpha \rho .