Polycyclic aromatic hydrocarbons in indoor and outdoor air of four typical homes in Hangzhou, China were determined with a highly automated chromatographic method. The results indicated that the concentrations of the 15 polycyclic aromatic hydrocarbons in the indoor air were between 1.907 microg/m3 and 14.29 microg/m3, which were much higher than those in the corresponding outdoor air. Because of the popular use of mothball in wardrobes, naphthalene had the highest concentration in all the 15 polycyclic aromatic hydrocarbons, which was up to 13.17 microg/m3 and contributed 68% to the total polycyclic aromatic hydrocarbons in the room. In kitchen, because of the representative cooking method, there had much of three- and four-ring polycyclic aromatic hydrocarbons. The indoor smoking not only led to high concentration of polycyclic aromatic hydrocarbons in the indoor air, but also contributed almost all the benzo(a)pyrene. Naphthalene, acenaphthene and pyrene were considered being generated by the indoor sources in all the four homes.