The epitaxial relationships of vapor deposited thin films of octithiophene onto KBr ( 001) were investigated by X-ray diffractometry. The temperature dependence of the film structure was examined between 25 degrees C and 125 degrees C. Two kinds of orientations, standing ( 100) and lying ( 51-1), were observed and the former orientation preferentially occurred at higher temperatures. The epitaxial relationships of both standing and lying orientations were determined. The observed epitaxial relationships were explained in terms of misfit ratio.