Applicability and user friendliness were initially tested by volunteers. The permeability of the polyurethane dressing from the outside to the inside for an aqueous solution was shown by incubating the outside layer with Rhodamine B. No fluorescence could be detected in the cotton pad beneath. A single dose experiment using theophylline as a model compound showed there was a delay in time before the substance could be determined in the pad. Drug content decreased with increasing time of patch application. When eight volunteers participating in methadone treatment were monitored, the substitute drug could always be detected in the patch associated with a minor concentration of EDDP (1,5-dimethyl-3,3-diphenyl-2-ethylidene-pyrrolidine). Indications of cocaine and heroin abuse were found in some of the patches investigated. Environmental contamination was not a critical point in the application of the transcutaneous collection device tested, provided the adhesive layer was carefully and smoothly affixed to the skin. There was no correlation between the amount of drug detected in a patch and the patient's daily methadone dose. The authors conclude that the so-called sweat patch appears to be a valuable tool in clinical and forensic toxicology, as it offers a longer and prospective surveillance period compared with blood and urine testing. 32 references, 1 table, and 2 figures