The elastic moduli of porous materials represented as a combination of spherical, cylindrical or disk shaped holes or solid elements was calculated using a self consistent method. A yield criterion could be found by stating that the elastic distortion energy evaluated with these moduli was equal to a critical value. Another yield criterion could be approximated from the results of finite elements computations using the homogenization technique. These criteria possess the same homogeneity as the yield criterion of the dense material. In the presence of a secondary population of smaller cavities the yield criterion was found to be different from the one obtained by simply adding the two volume fractions of holes. The hole growth rate deduced from these calculations was proportional to the equivalent strain rate and to the stress triaxiality ratio, inkeeping with the evolution of damage proposed by Iemaitre. This hole growth rate was enhanced by a population of small secondary cavities. In general the strain hardening and the damage are coupled. However for sintered porous nickel the introduction of an initial damage parameter proportional to the porosity suihced to describe the strain hardening behaviour. The condition for hole coalescence could not be connected to either a critical value of the porosity, or of the damage parameter, or a necking condition. The yield criterion modified by replacing the yield stress by the fracture stress could describe experimental results. Yet a critical local strain criterion also gave a good fit. The fracture toughness of syntactic foams could be explained by the local stress distribution in the glass spheres. In the case of ductile porous nickel the COD at initiation decreased as the fracture strain. This material exhibited a large tearing modulus whose decrease when the porosity was increased could be taken into account by the damage parameter. Fatigue crack propagation rates could also be rationalized with the use of the damage parameter and by reducing the surface of the material to be fractured.