Only a small number of resolved, single phosphorous, phosphodiester resonances are observed in the 31P spectrum of the 5S rRNA from E. coli. Its spectrum is much simpler than that of a tRNA (Gueron, M. and Shulman, R.G. (1975) Proc. Natl. Acad. Sci. 72, 3482-3484), which suggests that 5S RNA does not have a tightly folded, tRNA-like, tertiary structure. The resolved resonances in the 5S spectrum originate in loops D and E, near bases 88 and 76, respectively.