The microstructural modifications occurring during the natural or artificial aging of the aluminum alloys are related to modifications of physical properties such as electrical conductivity, hardness, and volume, each of them measured by specific instruments. In this paper the dimensional changes during the aging time were investigated through a high precision dilatometer; this technique keeps the sample at constant temperature and follows the precipitation phenomena versus time continuously. All the samples were taken from commercial thick plates of different aluminum alloys. The heavy plastic deformation during rolling was responsible for introducing anisotropy into the plate, so that the samples for the investigation were taken in the longitudinal, long transverse, and short transverse directions. By analyzing the dimensional changes of the samples versus aging time, standard and non-standard time-temperature values were selected as aging parameters for samples designated for mechanical and intergranular corrosion tests. The results obtained showed that the dilatometer can give important information about the precipitation kinetics occurring during aging, and it can be considered a useful instrumentation for the optimization of aging of aluminum alloys.