Abstract: Two modes of damage in composite laminates are considered:the intralaminar damage (matriz cracking) and the interlaminar damage(interior delamination).Using a vectorial representation of damage as internal variables in a phenomenological theory, relationship between the overall stiffness properties and the intensity of damage in the individual modes are determined.These relationships show that the intralaminar damage reduces all elastic moduli for a general orientation of the damage entities (cracks) and changes the initial orthotropic symmetry of a laminae.The interlaminar damage,however,does not change the symmetry but reduces the moduli.Predictions of the elastic moduli ehanges are compared with experimental results,showing excellent agreement.