The vibrational frequencies of a number of all trans polyenes H-(CH= CH)(n) - H ranging from n = 1 to n = 2 have been calculated within the density functional approach using a generalized gradient corrected exchange-correlation functional and a gaussian basis set. A remarkably good agreement with available experimental data is obtained. A correlation of the normal frequencies along the polyene series is presented describing the motions according to a nodal analysis. The results obtained are also correlated with the vibrations of an infinite polyenic chain.