Raman measurements and PM3 calculations of low frequency (<600 cm(-)) vibrational modes in a variety of different, fullerenes can be rationalized in terms of the multipolar "acoustic＇＇ oscillations of isotropic spherical and spheroidal shells. In this first of a two part series, we show that all fullerene cages have monopolar-like breathing vibrations. Within certain boundary conditions and in the absence of other data, the frequency of these vibrations may be used for cage size determination.