A graph-theoretical study of acyclic polyenes is carried out with an emphasis on the
influence of branching on several molecular properties. A definition of branching is given
and several branching indices are analyzed. The case of polyenes without a Kekulé
structure is discussed briefly. The main conclusions are:(a) thermodynamic stability of
conjugated polyenes decreases with branching, but (b) reactivity, in general, increases with
branching.