Allergy to house dust mites (HDM) and domestic pets is a major cause of asthma. People in developed countries spend more than 90% of their time indoors. We have measured levels of HDM allergen Der p I and cat allergen Fel d I in public buildings and public transport. Dust samples were collected by vacuuming a 1 m2 area for 2 min from five schools, six hotels, four cinemas, six pubs, three buses, two trains and 12 domestic households without a cat. Der p I and Eel d I were assayed with monoclonal antibodies in a two-site immunometric ELISA. Der p I concentration was-significantly higher in the private homes than in comparable sites in public places except for cinema seats (where high values were found) compared with domestic sofas. Der p I >2000 ng/g of fine dust was found in 30% of the upholstered seats, 9% having a concentration >10 000 ng/g. Fel d I levels were significantly higher in the dust from upholstered seats (geometric mean 14.88 μg/g) than in carpeted floors (geometric mean 0.73 μg/g), and in public places than in private homes. Eel d I >8 μg/g was found in 79% of the upholstered seats or furniture sampled in public buildings or public transport. In conclusion, upholstered seats from public buildings and public transport constitute an allergen reservoir for continuous contamination of the indoor environment which could compromise the effects of allergen avoidance employed at home.