The radial evolution of the amplitude of the Alfv¿nic fluctuations associated with the recurrent high-velocity solar wind streams has been usually considered to be consistent both with undamped fluctuations of solar orgin and with waves which saturate at some constant value of the ratio between the wave energy density and the background magnetic field energy density. In the inner solar system the two physical situations can be tentatively distinguished; indeed, according to theoretical models the saturated waves are expected to exhibit a more rapid decrease than the undamped ones. The Helios 1 and Helios 2 spacecraft observed a stream front during March 1976, whil they were coaligned along the streamlines. The radial evolution of the wave amplitudes might be considered to more consistent with saturated waves propagating between 0.41 and 0.65 AU. If true, such a conclusion would lead to the prediction that the contribution of the Alfv¿nic fluctuations to the energetics of the solar wind expansion may be appreciably larger than was previously estimated.