Cathodic peak potentials (E(p,c)) of twentyseven microbiologically active 2-phenyl-benzoxazole derivatives containing both electron withdrawing and electron donating groups on benzoxazole kernel and on phenyl moiety were measured by cyclic voltammetry in acetonitrile. The E(p,c) values were in the range of -2.8 V to -3.10 V except for those compounds which contained -NO2 substituent at position-5. Those benzoxazole derivatives possessing a NO2 group all had substantially lower reduction peak potentials, ranging from -1.60 to -1.80 V versus Ag-degrees/Ag+. The lowest unoccupied molecular orbital (LUMO) energies of these molecules were calculated by adopting the Huckel molecular orbital (HMO) approach. A linear relationship was found to be existing between the measured E(p,c) values and the calculated LUMO energies.