Concurrent sampling of PM 2.5 and PM 2.5-10 aerosols on a rooftop (15 m above ground) was conducted at a location in urban Urumqi (Xinjiang University 43°77'N, 87°61'E) during September 2010 to March 2011. These filters were analyzed for fifteen polycyclic aromatic hydrocarbons (PAHs). The ΣPAHs (sum of 15 PAHs) ranged from 0.11 to 1058.08 ng/m 3 in PM 2.5 and 0.01 to 90.89 ng/m 3 in PM 2.5-10 , respectively. 90% of the ΣPAHs existed in PM 2.5 . In the autumn the ΣPAHs ranged from an undetectable level to 10.93 ng/m 3 in PM 2.5 and 2.10 ng/m 3 in PM 2.5-10 , and in the winter from an undetectable level to 54.11 ng/m 3 in PM 2.5 and 5.12 ng/m 3 in PM 2.5-10 . Benzo(a)pyrene-equivalent carcinogenic potency (BaP eq ) was calculated to evaluate the cancer risk of carcinogenic PAHs to the public. The level of BaP eq in PM 2.5 was an average of 5.97 ng/m 3 , significantly higher than the value recommended by the WTO (1 ng/m 3 ). This suggests that it is important to control regional combustion sources to reduce air pollution-related health risks in urban Urumqi.