A complete homologous series of polyphenylene dendrimers up to the ninth generation (G9) corresponding to a theoretical molecular weight of 1.9 MDa was characterized by MALDI-TOF mass spectrometry. Mass spectrometry of synthetic polymers at extreme high masses is still uncommon to date and the underlying probable reasons are discussed. The measurements provided insight into the structural integrity, especially for the highest generations which could not be obtained by standard analytical tools for polymer characterization, such as gel permeation chromatography. The degree of structural integrity was elucidated by comparison of the measured molecular weights with theoretical molecular weights, calculated for the perfect structures. As a result, the dendrimers own structural perfection up to G4 and show increasing deviations with each higher generation starting at G5. The deviations could be partially attributed to a systematic error of the measurements but mainly to an increasing number of missing branches inside the dendrimers. The detected changes within the homologues series were discussed with respect to polymer-chemical aspects of the divergent route of dendrimer synthesis. Overall the whole dendrimer series shows very narrow polydispersity values below 1.005 which confirm the high structural integrity of these giant molecules up to a diameter of 33 nm, which can be considered as molecularly defined nanosized particles.