Abstract: The idea of extra dimensions is a very old one, but recent theoretical work has suggested the possibility that laboratory experiments at future colliders, or observations of cosmic rays, could actually access them.  This possibility, while unlikely, is so attractive for many reasons that it demands most serious consideration.  The most spectacular signature would be production of small black holes and their subsequent decay;  missing energy would be a less spectacular but still revolutionary signature.  I will discuss the phenomenology of the production and decay of black holes in high-energy particle collisions, assuming that the Planck energy is low enough to allow such experiments.