Ab initio, electron correlated calculations of the equilibrium geometries, dipole moments, and static dipole polarizabilities are reported for 10 heteroaromatic five-membered rings: furan, oxazole, isoxazole, all four oxadiazoles, both oxatriazoles, and oxatetrazole. Our geometries and dipole moments agree well with available experimental microwave determinations. The polarizabilities are expected to be accurate to within 5%. Structural isomerism affects the dipole moments strongly but the dipole polarizabilities are rather insensitive to it. Uncoupled Hartree-Fock calculations indicate that as much as half the polarizability comes from the σ-electrons. Simple empirical formulas based upon atom-and bond-additive models correlate the calculated polarizabilities of 20 five-membered heteroaromatic rings (10 azoles and 10 oxazoles) quite well. * Fax 506-453-4981; e-mail: ajit@unb.ca. X Abstract published in AdVance ACS Abstracts, April 15, 1996.Figure 1. Oxazoles with MP2/C dipole moments shown to scale, with the arrowhead pointing to the negative end.