Measurements of C1−C15 alkyl nitrates, perchloroethylene, and bromoform at two different sampling sites near Santa Cruz, CA, were conducted in 1995. The halocarbons were used as marker molecules to differentiate the air parcels collected into marine and continental groups. The average concentration of ∑n/i-C3−C12 alkyl nitrates at the California Coast (19.3 pptv) was lower than the levels obtained in the coastal mountains (53.9 pptv). This difference was shown to be most significant for the long chain n/i-C6−C12 alkyl nitrates. It is concluded that the ≥C6 alkyl nitrates in continental air can contribute 1−2% to the total NOy. The results are summarized together with earlier data sets to give a picture of contemporary levels and of the global occurrence of C3−C12 alkyl nitrates. In comparison with South Atlantic air (3.5 pptv), pattern analysis of n-alkyl nitrates suggests a marine source of primary n-alkyl nitrates. It is also shown that liquid chromatographic preseparation of the air sample extracts lea...