In contrast to other countries, there is an on-going debate but still no smoke-free legislation in Germany. Exposure to environmental tobacco smoke (ETS) in hospitality venues is assumed to be high, but air quality data are lacking. Therefore, the aim of our study was to perform a comprehensive exposure assessment by analysing the indoor air concentration of toxic or carcinogenic ETS compounds in restaurants, pubs, and discotheques. Active sampling of indoor air was conducted for 4 h during the main visiting hours in 28 hospitality venues. Polycyclic aromatic hydrocarbons (PAH), volatile organic compounds (VOC), aldehydes/ketones, and cadmium were analysed. In addition, particle mass concentration was assessed with two different methods and particle number concentration (PNC) was determined. Median nicotine levels were 15 microg/m(3) in restaurants, 31 microg/m(3) in pubs, and 193 microg/m(3) in discotheques. Across these three sampling site categories median levels of 3-ethenylpyridine ranged from 3 to 24 microg/m(3), median levels of benzene from 8 to 20 microg/m(3), median levels of cadmium from 3 to 10 ng/m(3), and median levels of the sum of 16 PAH according to US-EPA from 215 to 375 ng/m(3), respectively. Median PM(2.5) mass concentration assessed gravimetrically varied between 178 and 808 microg/m(3) and PNC between 120,000 and 210,000 particles per cm(3) in restaurants, pubs, and discotheques. The majority of the particles had a size of 0.01-0.5 microm. Concentrations of ETS compounds were always highest in discotheques. The strong correlation between ETS-specific markers (nicotine, 3-ethenylpyridine) and PM(2.5), PAH, VOC, aldehydes/ketones, and cadmium indicated ETS as main source of these toxic or carcinogenic substances. In conclusion, indoor air concentrations of ETS constituents were high in German hospitality venues and represented a substantial health threat. Effective measures to protect patrons and staff from ETS exposure are necessary from a public health point of view.