im a black belt in tkd and hav used head kicks on may occasions and they hav always worked 4 me. that may b because i am quite flexable and in an average street fight ur opponent does not really know how 2 block or fight. then again i spar a lot so u wud xpect mine 2 b good at them. But having fought agains other martial artists e.g wing chun, boxers and judo they have always worked.