Concerns of Rillito citizens about emissions of dioxins and furans from the Arizona Portland Cement Plant and stack testing at APCC led to an ambient air monitoring program conducted in 2004 - 2005. Ambient concentrations of dioxins and furans proved to be within health-based guidelines. These concentrations were somewhat higher than those measured at background sites but considerably lower than at urban sites. The distribution of the 17 toxic dioxins and furans in the ambient air of Rillito closely resembled the mobile source profile but was quite different from the APCC profile. The dioxin and furan concentrations measured during the one-year study suggested that mobile source emissions had a much greater impact at Rillito than the cement plant emissions.