The five revised validation guidelines include: (1) general considerations for validation of the DNA analysis procedure; (2) developmental validation; (3) internal validation; (4) material modification; and (5) performance check of established procedures. The validation section of the Guidelines for a Quality Assurance Program for DNA Analysis by the Technical Working Group on DNA Analysis Methods has been revised due to increased laboratory experience, the advent of new technologies, and the issuance of the Quality Assurance Standards for Forensic DNS Testing Laboratories by the Director of the Federal Bureau of Investigation (FBI). This paper provides revised validation guidelines and definitions approved by the Scientific Working Group on DNA Analysis Methods (SWGDAM) on July 10, 2003.