Indoor NO2 concentrations were measured in the kitchen, the living room and bedroom of 612 houses in two different areas in the Netherlands. In asub-sample, personal exposure of the housewives to NO2 was measured. NO2concentrations indoors depended on the presence or absence of (un)vented gas appliances. Personal NO2 exposure was only different between the two areas in the group with the lowest indoor concentrations. It was concluded that with respect to NO2 exposure it is impossible to categorize groups without accounting for gas appliances inside the house.