Beginning with his initial studies of the angular dependence of the spectra of electrons emitted in ion‐atom collisions, the first measurements to provide a detailed and comprehensive description of the collisional ionization process, M. Eugene Rudd contributed to an impressive list of ‘‘firsts’’ in the study of collision physics. In 1963, Gene published the first observation of a two‐center phenomena in collision physics, although it was several years before the features he observed in the spectra of ejected electrons were clearly interpreted as contributions from electron‐capture‐to‐the‐continuum, a two‐center phenomena. He contributed firsts in studies of doubly differential cross sections, inner‐shell‐ and auto‐ionization, interactions involving dressed projectiles, and interactions of ions and photons with surfaces. He also refined the experimental techniques to provide data of improved reliability in many areas where others had made pioneering studies including measurements of doubly‐differential cross sections for incident electrons and total‐ionization and charge‐transfer cross sections for ion impact. ©1996 American Institute of Physics.