The electron energy loss spectrum of adenine has been recorded over an excitation energy range of approximately 3-22 eV for scattering angles of 3 degrees and 6 degrees. In addition to reporting accurate vapor phase peak positions, the present work supports the long-held contention that the group of peaks in the 6- to 10-eV range belong to transitions that originate from valence pi orbitals. In the vapor phase spectrum, a Rydberg transition corresponding to an n----3s excitation is readily observed with a term value of 3.45 eV relative to the first long-pair ionization potential.