We perform a near-field mapping of Bloch Surface Waves excited at the truncation interface of a planar silicon nitride multilayer. We directly determine the field distribution of Bloch Surface Waves along the propagation direction and normally to the surface. Furthermore, we present a direct measurement of a near-field enhancement effect under particular coupling conditions. Experimental evidence demonstrates that a ∼ 102 near-field intensity enhancement can be realistically attained, thus confirming predictions from rigorous calculations. © 2008 Optical Society of America.