Little is known regarding the use and ambient levels of pesticides in Chilean agricultural regions. Chlorpyrifos (CPF) is one of the most used active ingredients in Chile and in the world. However, few investigations have been conducted to understand its environmental distribution and fate. In this study, PUF disk passive air samples were deployed during similar to one year in two areas, Angol (5 sites) and Villarrica (2 sites), in the Araucania Region. The concentration in air of CPF ranged from ten to thousands of pg m(-3) (similar to 20-14 600). The highest CPF concentrations were detected at the Angol sites (similar to 14 600 pg m(3)) during period 2 (August-December 2008). These results were higher by a factor of similar to 10-15 than those detected in Villarica sites (similar to 2000 pg m(3)) in period 1 (April-July 2008). Seasonal CPF variations were observed, at both sites, within the sampling periods. Air back trajectory analyses showed that air masses from nearby agricultural zones contributed most of the CPF detected in Angol sites when the wind speed was low and at Villarrica when those sources were likely located north of the VMA site. These results provide initial data for CPF in the Chilean atmosphere and contribute new information to understanding distribution of CPF in Chilean environments.