A quintet ground-state bisnitrene, 1,3-dinitreno-5-nitrobenzene, was studied by randomly oriented ESR spectroscopy as part of our project to study purely organic magnetism and supramolecular functionality expected for high spin systems. An observed ESR spectrum of the bisnitrene was interpreted using S=2, g=2.003, D=0.224 cm(-1), and E=0.038 cm(-1). The determined fine-structure parameter D and E values are in accord with our semiempirical treatment for the quintet state in terms of the fine-structure tensor of the triplet state of p-nitrophenylnitrene. In this work, we emphasize that all the documented fine-structure parameters D and E for quintet bisnitrenes do not reproduce the corresponding observed fine-structure ESR spectra from random orientation.