INTRODUCTION This study@ conducted for the American Petroleum Institute@ was designed to evaluate the embryotoxic and/or teratogenic potential of Methylt-butyl-Ether in the rat . The test substance was administered by the inhalation route at exposure levels of 250@ 1000 and 2500 ppm. Test substance was administered 6 hours per day@ daily from Day 6 to 15 of gestation@ a 10-day period. Species and strain of test animal@ exposure levels and route of test substance administration were established by the sponsor. Testing was conducted at Bio/dynamics@ Inc.@ Mettlers Road@ East Millstone@ New Jersey U8873@ Raw data will be stored in the archives of Bio/dynamics Inc.