In recent years, more and more people have started to recognize the importance of indoor air environment. In order to obtain the comprehensive knowledge about the indoor environment situation and find out the main source of indoor air pollution, 550 residents living in different buildings/apartments were subjected to a questionnaire survey and field measurements were conducted in 30 of these buildings/apartments in Dalian from January to February 2002. From the questionnaire survey and field measurements, we found that many residential buildings had good outdoor surroundings. Dust and automobile emissions are main sources of outdoor air pollution. Though air tightness of these buildings is fairly good, outdoor air quality still has great impact on indoor air environment. The most serious indoor air pollutant is formaldehyde which is mainly caused by decoration. (C) 2004 Published by Elsevier B.V.