Abstract The syntheses of α,ω-di(2-phenanthryl)-, di(3-phenanthryl)-, and di(9-phenanthryl)polyenes (In, In′, and In″, n=1–6) by means of the Wittig reaction are described. Formylphenanthrenes (II, II′, II″), phenanthrylpropenals (III′, III″), phenanthrylpentadienals (IV, IV′, IV″) and muconaldehyde (VIII) were used as carbonyl components in the reaction. Phenanthrylmethyl-, phenanthrylpropenyl- and phenanthrylpentadienyltriphenylphosphonium bromides and l,4-bis(triphenylphosphonium)-2-butene dibromide were converted into phosphoranes (V, V′, V″, VI, VI′, VII″, IX, IX′, IX″, VII) by a reaction with phenyllithium. The reaction of carbonyl components with phosphoranes with a proper combination yielded diphenanthrylpolyenes (In, In′, In″). 2- and 3-Phenanthryl derivatives (In and In′) exhibited electronic spectra with well-defined vibartional fine structure, whereas 9-phenanthryl derivative (In″) showed broad and structureless absorption curves. It was found that the plots of the longest-wavelength maxima (λmax) of In and In′ against n0.6 and n0.8 give excellent straight lines which can be given by the empirical formulas: In:λmax=57.9n0.6+303 nm (in tetrahydrofuran) In′:λmax=30.3n0.8+348 nm (in tetrahydrofuran)