The concentrations of 15 volatile organic compounds (VOCs) including 1,3-butadiene, benzene and styrene were measured in a wide range of indoor and outdoor urban microenvironments. For all VOCs, excluding naphthalene, mean concentrations in cars exceeded those at heavily trafficked roadside locations. Concentrations were higher indoors, with no correlation observed between indoor and outdoor concentrations. Thus, in poorly ventilated buildings, indoor emission source strength is considered a more significant influence on concentrations of VOCs in indoor air than outdoor air concentrations. In the 6 smoking homes studied, environmental tobacco smoke was found to make a substantial contribution to concentrations of 1,3-butadiene.