Findings show the usefulness of using sweat patches to complement traditional testing, as sweat patches provide a longer detection span. Quantitative analysis was not possible with sweat patches, because the amount of sweat secreted varied, depending on a number of variables. Measurement of the volume of the sweat was not possible. All of the patches showed positive results for methadone, and 70 percent showed positive for EDDP; nicotine, cotinine, and caffeine were detected. Cocaine was detected in two specimens. No false positive results were obtained for drug-free samples. All urine and saliva samples showed positive results for methadone. Neither opiates nor cocaine were found in saliva or urine. Fifty percent of urine samples were also positive for cannabinoids, and 30 percent for benzodiazepines. All hair samples were positive for methadone, but opiates were never detected. The analysis of sweat may be an alternative, non-invasive means for verifying drug history and for monitoring compliance easily and quickly. It is also difficult to adulterate. Sweat patches from Medical Europe Diagnostic in Madrid, Spain, were applied to 10 heroin addicts and 3 drug-free volunteers. The patches were worn for approximately 1 week; urine, saliva, and hair samples were collected at the time the patches were removed. Sweat extracts from the patches were directly analyzed by gas chromatography/mass spectrometry for the presence of nicotine, cotinine, caffeine, methadone, EDDP, and cocaine. The extracts were subsequently derivatized to detect benzoylecgonine, ecgonine methyl ester, morphine, codeine, and 6-acetylmorphine. 4 tables, 1 figure, and 11 references