[en] A resonance radiationless energy transfer process has been found between the excited state of diphenylmethylene (a molecule with a triplet ground state) and fluorescein in a rigid alkaline glass at 77⁰K. By measuring the effect of fluorescein on the lifetime of excited diphenylmethylene, the critical transfer distance R₀ was found to be 61 A. This compares favorably with the theoretical value of 50 A calculated by the Forster weak-interaction dipole treatment. This is the first example of the dipole-allowed radiationless energy transfer of the type ³D* + ¹A → ³D + ¹A*. 3 figures