Lyons has notably advanced knowledge of the electronic and electrical properties of molecular crystals. Following extensive experimental and theoretical studies, he proposed an energy level scheme for electrically active crystals that has become widely accepted. He predicted the heights of the intrinsic conduction levels of a number of crystals on this basis, and subsequent experiments have confirmed the values. This success has established the value of Lyons's model, and opens the way to new advances. He has also made important experimental contributions to knowledge of gas phase electron capture by large molecules, to the measurement of ionization energies, and to studies of exciton-exciton collision processes.