The discovery, in the mid-1990s, of a variety of internal transport barriers(ITBs), capable of lowering transport down to neoclassical values, has beenone of the major steps forward in the progress of plasma confinement. Thesephenomena, which usually show reduced transport together with the suppressionof some instabilities, also offer a means to improve our understanding of theunderlying processes which control the anomalous transport in toroidal plasmaconfinement devices.An understanding of ITBs requires extensive and detailed experiments, whichimply new challenges for the diagnostic community. The present paper attemptsto outline the main advances achieved as well as the prospects for improvementon selected diagnostics oriented towards ITB physics. We will concentrate onthe latest achievements in three systems, each of them concerning,simultaneously, several parameters in the growth rate againststabilization/decorrelation processes (electric fields, sharp gradients andturbulence): heavy-ion beam probe (mainly a monitor for electric fields, butalso able to provide fluctuation measurements of density and plasmapotential), microwave reflectometry (used for turbulence and density profilestudies) and a `classical' core diagnostic with capabilities to resolve sharpgradients and detailed structures in the density and temperature profiles,high-resolution Thomson scattering.