The analysis of exhaled air has several advantages since it is a noninvasive method applicable to a large number of toxic agents, in addition to being a simpler matrix than those of other biological samples such as urine and blood. However, it presents some challenges, such as the necessity of a more sensitive sampling procedure, since the chemical substances eliminated through exhaled air are unchanged in form, not being metabolized, and exhaled compounds are present at extremely low concentrations, i.e. in the nanomolar range. To improve the sensitivity and precision of measurement of the concentration of these substances in exhaled air, the sample usually has to be concentrated before assay by gas chromatography. To this end, the use of the solid-phase microextraction (SPME) technique has been proposed as an efficient sampling method. This paper presents a revision of breath analysis as a biomarker for occupational and environmental exposure to chemicals. The sampling methods and the potential use of SPME for determining chemical substances in exhaled air are discussed.