This bill amends title 38, United States Code, to expand eligibility for a presumption of service connection for certain diseases among veterans. Specifically, it targets veterans who served in Guam and were exposed to herbicide agents, such as Agent Orange. The legislation modifies existing law by defining a specific period for service in Guam or its territorial waters, from August 15, 1958, to July 31, 1980 . This change ensures that veterans who served during this timeframe are explicitly covered for the presumption of service connection for conditions associated with herbicide exposure, aligning their benefits with those for other similarly exposed veterans.