The reaction of 1,1-diphenylethylene with sulphur yields benzothieno[2,3-b]benzothiopene (I), together with 3-phenylbenzothiophene. Oxidation of I with aqueous peracetic acid gives the corresponding monosulphone (III) and disulphone (IV). The structures of I and its derivatives were established by chemical reactions and electronic and NMR spectra. The structure of the parent compound I was determined by X-ray analysis. The aromatic character of the condensed thiophene system (I) was demonstrated by chemical reactions as compared with those of the corresponding sulphones, and from the observed bond lengths obtained from the X-ray analysis of I.