Dedicated to Edgar Heilbronner on the occasion of his 80th birthday Electron-transfer processes that involve single and doubly charged cations of corannulene (C 20 H 10 ) and coronene (C 24 H 12 ) are examined by three different mass-spectrometric techniques. Photoionization studies give first-ionization energies of IE(C 20 H 10 ) 7.83 AE 0.02 eV and IE(C 24 H 12 ) 7.21 AE 0.02 eV. Photoionizations of the neutrals to the doubly charged cations occur at thresholds of 20.1 AE 0.2 eV and 18.5 AE 0.2 eV for corannulene and coronene, respectively. Energy-resolved charge-stripping mass spectrometry yields kinetic energy deficits of Q min (C 20 H 10 13.8 AE 0.3 eV and Q min (C 24 H 12 12.8 AE 0.3 eV for the transitions from the mono-to the corresponding dications in keV collisions. Reactivity studies of the C 20 H 2 10 and C 24 H 2 12 dications in a selected-ion flow-tube mass spectrometer are used to determine the onsets for the occurrence of single-electron transfer from several neutral reagents to the dications, affording two different monocationic products. With decreasing IEs of the neutral reagents, electron transfer to doubly charged corannulene is first observed with hexafluorobenzene (IE 9.91 eV), while neutrals with lower IEs are required in the case of the coronene dication, e.g., NO 2 (IE 9.75 eV). Density-functional theory is used to support the interpretation of the experimental data. The best estimates of the ionization energies evaluated are IE(C 20 H 10 ) 7.83 AE 0.02 eV and IE(C 24 H 12 ) 7.21 AE 0.02 eV for the neutral molecules, and IE(C 20 H 10 ) 12.3 AE 0.2 eV and IE(C 24 H 12 ) 11.3 AE 0.2 eV for the monocations.