Eight aromatic hydrocarbons were quantified in a newly constructed building before occupancy during the period of November 1997 to January 1998. Air samples were collected in 6 L stainless steel canisters for 8 hours based on working hour. It was found that the measured total concentration of aromatic hydrocarbons decreases rapidly with time up to a steady-state value. However, the fractions for each aromatic hydrocarbon were greatly changed with time. The concentration ratios of indoor to outdoor for aromatic hydrocarbons are greater than 1 during early period of the measurement, and the ratios decrease with time. The concentrations of toluene, m+p-xylene, ethylbenzene, and o-xylene are much higher than those of styrene, 1, 2, 4-trimethylbenzene, and 1, 3, 5-f trimethylbenzene in indoor air. The concentration fractions of m+p-xylene, ethylbenzed, and o-xylene in indoor air are about twice as hight as those in outdoor air measured during the similar period. It was concluded that the aromatic hydrocarbons were emitted from building materials, paints, and adhesives in an-built building.