AbstractThe age dependence of the velocity dispersions σv(τ) of the nearby stars is considered under distinct assumptions on the history of the star formation rate. The velocity distributions N¦U¦, N¦V¦, N¦W¦ are derived from this by means of the diffusion theory using the standard case by WIELEN AND FUCHS (1983a) and are compared with the observed distributions of a kinematically unbiased sample of nearby stars. The best agreement is found for a nearly constant star formation rate.