Three- to six-ring polycyclic aromatic hydrocarbons in the vapor phase (PAHs/sub vap/) and in the particulate phase (PAHs/sub pat) and total suspended particulate (TSP) in ambient air were sampled and determined year-round. At ambient temperature levels, substantial amounts of three-to five-ring PAHs were found in the vapor phase depending upon temperature (T, K) and the six-ring PAHs were all found in the particulate phase. For three- to five-ring PAHs, the Langmuir adsorption concept was introduced for PAHs/sub vap/ and PAHs/sub pat/ on the particulates. log ((PAHs/sub vap/) /)(PAHs/sub pat/) / (TSP))) was related to 1/T, and a high correlation (r = 0.834 to -0.942) was obtained between the two quantities. Thus, aspects of the three- to five-ring PAHs in ambient air were considered to be explained by using the Langmuir adsorption concept.