The invention relates to a method for analyzing masks for photolithography. In this method, an aerial image of the mask for a first focus setting is generated and stored in an aerial image data record. The aerial image data record is transferred to an algorithm that simulates a photolithographic wafer exposure on the basis of this data record. In this case, the simulation is carried out for a plurality of mutually different energy doses. Then, at a predetermined height from the wafer surface, contours which separate regions with photoresist from those regions without photoresist are in each case determined. The result, that is to say the contours, are stored for each of the energy doses in each case in a contour data record with the energy dose as a parameter. Finally, the contour data records are combined to form a three-dimensional multicontour data record with the reciprocal of the energy dose as a third dimension, and, on the basis of the transitions from zero to values different than zero in the contours, a three-dimensional profile of the reciprocal of the energy dose depending on the position on the mask is generated. This profile, the so-called effective aerial image, is output or stored or automatically evaluated. The same can also occur with sections through said profile.