The ionized trails of faint meteors have been investigated by observation of radio echoes at two spaced receiving stations. The mean ionization curve is much shorter than predicted by present theory, and in particular the rise to maximum electron line density is more rapid than expected. Occasional meteors appear almost instantaneously with maximum electron density, and in many cases irregularities in the ionization considerably distort the diffraction effects during trail formation. Evidence for the fragmentation of meteors is also presented. These effects are considered in relation to Jacchia's photographic observations of the light curves of faint visual meteors.