Two-dimensional heteronuclear chemical shift correlation, heteronuclear relayed coherence transfer and autocorrelated 13C—13C double quantum coherence have been used to assign the proton and 13C NMR spectra of benzo[b]phenanthro[4,3-d]thiophene. The highly complementary nature of the heteronuclear relay and carbon–carbon double quantum spectra conveniently provides the means of avoiding breaks in the carbon–carbon connectivity network assembled by the latter, which may arise when strongly AB rather than AX carbon–carbon pairings are encountered. Nuclear Overhauser difference spectra have shown the title compound to possess a tertiary helical structure similar to that of phenanthro[3,4-b]thiophene; the average separation between the H-1 and H-13 atoms of the title compound was found to be 2.06 ± 0.04 Å.