Perchloroethylene (PCE) is the most widely used solvent in dry-cleaning; it is toxic to the liver, kidney and central nervous system and may be a human carcinogen. PCE levels in the ambient air of dry-cleaners' homes were measured, and samples of end-exhaled air (alveolar air) from subjects who were not themselves occupationally exposed, but who were members of the household of dry-cleaners were compared with samples from the general population. Thirty apartments were visited housing dry-cleaners and their families, and located well away from the dry-cleaning premises. Indoor air samples and alveolar air samples were collected contemporaneously from the dry-cleaners (36) and members of their household (34). The same sampling procedure was followed in 25 private homes where samples of alveolar air were collected from 41 subjects who were not occupationally exposed and who acted as control group. All the samples were analysed by direct-injection gas-chromatography. PCE levels in dry-cleaners' homes proved to be significantly higher than in control houses (geometric means: 265 vs. 2 micrograms/m3, P < 0.001). PCE levels in the alveolar air exhaled by dry-cleaners, their family members and control subjects were statistically different (geometric means: 5140, 225 and 3 micrograms/m3, respectively; P < 0.001). PCE is a ubiquitous substance in indoor air, but is present at higher concentrations in apartments where dry-cleaners and their families live. Biological monitoring of PCE in alveolar air confirms that family members of dry-cleaners are more exposed than the general population.