<qa>  What is the most frequently abused intoxicant in the United States?Ethanol continues to be the most frequently abused intoxicant in the United States.4 Drug testing in various work environments has become commonplace during the past two decades and will at times include blood, breath, or urine alcohol testing.5 While valid reasons for false positive drug tests do occur, a plethora of unusual and dubious explanations have been likewise tendered. Medical Review Officers MRO involved in evaluating such reports rely on past case reports, knowledge of laboratory analytical techniques, and other scientific evidence to validate or negate claims of drug use in the workplace. ABHS are now found in most hospitals and health-care facilities.1,3 Only one human report of serum ethanol levels following frequent clinical use of the ABHS has been reported.7 This finding of a negative serum ethanol level in this case is likely to be reproducible in all clinical settings as the physician attempted to simulate the most extreme use of the product that would be consistent with labeling instructions. Since alcohol breathalyzer testing is based upon exhaled portions of ethanol found within the blood stream, this method of testing would likely be negative as well. 