We report here electrogenerated chemiluminescence (ECL) observed upon oxidation of aromatic hydrocarbons with different potentials for oxidation to the radical cations (D+.) and tri-n-propylamine (TPrA) in MeCN/benzene solutions. In this system, with TPrA as a coreactant, ECL is generated by reaction of D+. with the free radical intermediate produced upon oxidation of TPrA. ECL was observed from three out of the eight compounds studied. On the basis of the energetic criterion for ECL, the potential for oxidation of the intermediate free radical, Pr2N(CH.)Et, was found to be about -1.7 V vs SCE. By studying the fluorescence quenching of several polycyclic aromatic hydrocarbons (PAHs) by TPrA, the standard potential for oxidation of TPrA to TPrA(+.) was estimated as 0.9 V vs SCE.