AbstractAnesthesia of the caudal margin of the nose and the upper lip is of considerable importance to otolaryngologists. It follows, therefore, that the sensory innervation is also important. In situations where adequate anesthesia is needed and limited quantity must be used, it is advantageous to know where that limited amount could be best placed to accomplish the greatest anesthesia.Due to transmedian innervation of the upper lip by the infraorbital nerves, it may be necessary to block both sides when procedures are to be carried out in the vicinity of the midline. The infraorbital nerves of each side cross the area of the frontonasal process and ultimately decussate in the midline. No other nerves were found to participate in sensory innervation of the upper lip.