Stellar magnetic fields including a strong dipole component are believed
to play a critical role in the early evolution of newly formed, low mass
stars (T Tauri stars) and their circumstellar accretion disks. Due to
their youth and low mass, the stars are generally fully convective. It is
currently believed that the stellar magnetic field truncates the accretion
disk several stellar radii above the star. This action forces accreting
material to flow along the field lines and accrete onto the star
preferentially at high stellar latitudes. It is also thought that the
stellar rotation rate becomes locked to the Keplerian velocity at the radius
where the disk is truncated. I will review recent efforts to measure the
magnetic field properties of T Tauri stars, focussing on how the observations
compare with the theoretical expectations. A picture is emerging indicating
that quite strong fields do indeed cover the majority of the surface on these
young stars; however, the dipole component of the field appears to be
surprisingly small. I also discuss how the observations compare to
predictions from models of dynamo magnetic field generation in fully
convective stars.