[en] The triple radio source 3C 154 is centered on a 17.5 mag QSO with z=0.580. The optical spectrum is Seyfert-like. The outer radio lobes are separated by 43'', or about 375 kpc (for H0=50, q0=0) in projection, making 3C 154 among the larger sources in linear size. We have used a simple expansion model to determine that the characteristic outburst time scale is longer than 6 million years