The photochemical behavior of mixtures of selected sulfur containing species, hydrocarbons, and nitrogen oxides was examined in outdoor smog chambers. Sulfur dioxide, H2S, CH3SH, COS, and thiophene are the sulfur species tested. A surrogate ambient hydrocarbon mixture comprised of 25 percent propene and 75 percent butane known as the EKMA mix was selected. An experimental matrix was designed where initial EKMA mix concentrations ranged from 0.0 to 2.0 ppmC, initial NOx concentrations ranged from 0.0 to 0.4 ppm, resulting in initial HC/NOx ratios of 0. to 40. The impact of the sulfur species on the behavior of the EKMA Mix-NOx system was examined by conducting experiments at various points on the matrix with and without 1 ppm of each sulfur species. A total of 172 single-chamber experiments was conducted over 43 test days. The experimental results were analyzed to determine the impact of each test sulfur species on the production of ozone, SO2 (where appropriate), and particulate sulfur. In selected cases, the influence of each test species on the average hydroxyl radical concentration was examined.