I thank Dr Fraser for pointing out his work with alprazolam. We reported encountering patients receiving methadone maintenance therapy who abused alprazolam. Toxicological examinations of their urine specimens, using thin-layer chromatography, had not detected alprazolam. The laboratory is presently using both thin-layer chromatography and EMIT methods to screen urine specimens for benzodiazepines. My experience with the EMIT system in detecting regular alprazolam abuse by those receiving methadone is good. However, I have worked with two patients receiving methadone maintenance therapy who reported episodic abuse of alprazolam. Using the EMIT method, results of the toxicological examination of their urine specimens were negative for benzodiazepines until the patients began to regularly abuse alprazolam. Initially, the patients periodically abused alprazolam to "boost the effect" of methadone. They ingested alprazolam immediately after being medicated with methadone but several days before the urine toxicology examinations. Stitzer and colleagues1 have reported this "boosting"