A phosphorescence theory for aromatic molecules is formulated in terms of the equations-of-motion method. The theory is applied to the INDO/S calculations on the lowest tripler radiative lifetime of benzene. All the calculations are performed within the spin-same-orbit interaction approximation. The random-phase approximations are found to give better results than the Tamm-Dancoff approximation (or the singly excited CI). The importance of the spin-other-orbit interactions contributing to the phosphorescence lifetime is discussed from the formula derived in an Appendix.