A method of manufacturing a projection objective (22) of a microlithographic projection exposure apparatus (10). The projection objective (22) comprises at least one mirror (M1 to M6) that each have a mirror support (241 to 246) and a reflective coating (26) applied thereon. First imaging aberrations of a pre-assembled projection objective are measured. Before the coating (26) is applied, the mirror supports (241 to 246) are provided with a desired surface deformation (34). If the mirrors (M1 to M6) are not reflective for projection light without the coating (26), measuring light is used that has another wavelength. Alternatively, two identical mirror supports (246) may be provided. One support having a reflective coating is part of the pre-assembled projection objective whose imaging aberrations are measured. The other support is provided with surface deformations before coating and mounting the support into the objective.