AbstractIon-neutral chemistry in Titan's upper atmosphere (~ 1000 km altitude) is an unexpectedly prodigious source of hydrocarbon-nitrile compounds. We report observations from the Cassini Ion Neutral Mass Spectrometer (INMS; Waite et al. 2004) and Cassini Plasma Spectrometer (CAPS; Young et al. 2004) that allow us to follow the formation of the organic material from the initial ionization and dissociation of nitrogen and methane driven by several free energy sources (extreme ultraviolet radiation and energetic ions and electrons) to the formation of negative ions with masses exceeding 10,000 amu.