The conformational properties of octakis(phenylsulfanyl)naphthatene (ophn) were examined by their X-ray structural and thermal analyses. Ophns have been prepared in two different conformations, i.e. the red and yellow forms. The yellow form consists of the aabbaabb and bbaabbaa isomers (the descriptions a and b denote side-chain phenyl moieties projecting above or below, respectively). Both isomers are alternately arrayed in the direction parallel to the c-axis. This crystal structure will not be formed with only the chiral compounds. From the DTA results, the crystal melting point (T-m1) of the red form appeared at around 201.3 degreesC, for the yellow form, T-m2 appeared at around 174.5 degreesC and the crystallization point (T,2) is 114.5 degreesC. Both crystals indicate an amorphous phase during cooling after melting, then the T-g = 60 degreesC. The phase transformation observed for the red and yellow forms is summarized on the basis of the thermal analysis and powder X-ray diffraction pattern.