Abstract: The present invention is a biometric recognition method and system for identifying humans and animals with acoustic scanning techniques. The invention is based upon transmitting acoustic energy through an external accessible surface to non-visible internal tissue having a unique distinguishing characteristic. A master representative pattern of the unique distinguishing characteristic is produced by the interaction of an acoustic energy beam with discontinuities and inhomogeneities within the non-visible internal tissue. The master representative pattern is used for reference and compared to a current representative pattern formed upon each attempted reentry into the system.