FTIR spectra of a series of bis-diacetylenes were studied. An absorption at about 2255 cm-1 due to stretching vibrations of the diacetylene system (observed in all cases as a relatively intensive peak) has been found to be very characteristic for these diacetylene derivatives, as well as a strong coupling of the CH2 wagging vibration modes resulting in splitting of the absorption peaks at 1300-1360 cm-1.