In response to a congressional request, GAO reviewed selected aspects of the Strategic Defense Initiative Organization's (SDIO) Space-Based Chemical Laser (SBCL) Research Program, specifically: (1) SDIO progress and changes in SBCL research; (2) whether changes in SBCL research priorities were detrimental to other laser research; and (3) Department of Defense (DOD) and SDIO actions to determine SBCL compliance with the Anti-Ballistic Missile Treaty. GAO found that: (1) the original SDIO laser research schedule has slipped up to 2 years, with some work eliminated or significantly reduced; (2) although SDIO has built a laser, it has not produced a beam, developed beam control, or completed a tracking system; (3) SDIO built the primary SBCL mirror, but the mirror needed repairs and modifications for space operation; (4) SDIO indicated that SBCL and other research priorities remained unchanged; and (5) SDIO did not emphasize SBCL to the detriment of other laser technologies. GAO also found that: (1) SDIO planned to use a chemical laser experiment as a demonstration of U.S. potential to counter possible Soviet responses to SBCL deployment; (2) SDIO plans to space-test a laser technology 4 years earlier than originally scheduled, but the launch date has slipped; and (3) DOD determined that the proposed experiment complied with the traditional or restrictive interpretation of the Anti-Ballistic Missile Treaty.