BERGER J., AVRON J. A Classification Scheme for Toroidal Molecules (42K, LaTeX) ABSTRACT. We construct a class of periodic tilings of the plane, which corresponds to toroidal arrangements of trivalent atoms, with pentagonal, hexagonal and heptagonal rings. Each tiling is characterized by a set of four integers and gives rise to an infinite family of toroidal molecules. These may be chosen to fit a desired shape, size or number of atoms in the molecule. The configurational energy and the delocalisation energy of several molecules obtained in this way were computed for Tersoff and H\"uckel models. The results indicate that many of these molecules would be stable. We studied the influence of size on the H\"{u}ckel spectrum: it bears both similarities and differences as compared with the case of tubules.