We have recently produced surface magnetic field maps for two actively accreting G and K-type classical T Tauri stars with ages of 3-5 Myr. By comparison with maps published for two other classical T Tauri stars we find that there appears to be a relationship between increasing complexity in field distributions and increasing radiative core sizes.
We discuss the implications of these results for magnetospheric accretion and for the evolution of magnetic fields in intermediate mass stars as they evolve onto and along the main sequence.