A 24-month study was undertaken to characterize the indoor residential air quality. Seventeen residential dwellings were monitored, each for a 14-day period. Air samples were collected from four locations: one outdoor site adjacent to the building; and three indoor sites, the kitchen, bedroom, and living room. 'Continuous' sampling was carried out for CO, SO2, NO, NO2, CO2, O3, CH4, and THC. TSP, RSP, SO=4, NO-3, Pb, ammonia, and aldehydes were monitored intermittently. Aerosol samples were collected for elemental analysis by the Proton Induced X-ray Emission (PIXE) technique. In addition, data on energy parameters, infiltration rates, and family activities were obtained by observations, field experiments, and daily questionnaires, respectively. Each residence was monitored with minimal interference in the daily activities of the occupants; thus, the residential pollutant concentrations were determined under real-life conditions. Finally, the relationship between energy conservation measures and air quality in the indoor environment is examined. The observed indoor air pollutant concentrations were, on the average, not very high; however, persistent moderate and, at times, elevated pollutant levels were observed. The lack of studies concerning the health implications of such levels is briefly discussed.