Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF/MS), size exclusion chromatography (SEC), and dilute solution viscometry were used to analyze the structure of three generations of Astromol (trademark of DSM) dendrimers having cyano end groups. The molecular weights, the defect contents, and. the structures of the "imperfect" dendrimers were determined by MALDI/TOF/MS analysis with fractions collected using a SEC fraction collector. The peak broadening observed for these materials in SEC was studied by adding different co-solvents to the SEC mobile phase. The hydrodynamic radius of the dendrimers was measured both by dilute solution viscometry and by SEC universal calibration. Our radii data are comparable to previously published results for these dendrimers obtained by neutron scattering and support the opinion that dendrimers have compact spherical structures.