Drugs are incorporated into sweat by passive diffusion and transdermal migration. The proof of principle of drug testing in sweat has been developed in the past 25 years. Numerous devices and approaches have been developed for the collection of sweat. The potential application of sweat analysis for on‐site drug testing at the roadside is limited by the nonavailability of adequate analytical devices. Their major limitation is the lack of sensitivity to some drug classes, an aspect that has been improving over the years. Adequate analytical methodology has been developed for drug analysis both in sweat patches and skin swabs. Immunoassays directed at the detection of parent drugs combined with highly sensitive chromatographic coupled to mass spectrometry analytical methods is the most common analytical approach. In particular, the sweat patch drug testing approach has been proven to be an alternative to urine testing in substance abuse treatment and probation programs. Some of the advantages include a wider detection window, easier sample collection, and reduced opportunities for sample tampering. There are still some pending studies on environmental skin contamination, drug absorption/loss through patch membrane, and drug reabsorption from patches that limit the routine application of drug testing in sweat to some extent.