Results from a unique experimental system that quantifies combustion products from a single diesel combustion event are presented and the implications of these results are discussed. Data presented in this paper are the emission levels for carbon monoxide and nitric oxide, normalized by carbon dioxide produced, as a function of fuel quantity injected. Carbon monoxide is notably present in very short duration ( or small mass) injection burns where the spray event concludes before the beginning of the major heat release. However, the trend for NO emission levels appears to be influenced by the interaction of combustion with injection. For events with an overlap between injection and the combustion event, reduced NO emission levels are observed. Examination of data from engines indicates a similar trend in NO emission behavior; residence time effects and/or entrainment of post combustion gases into the fuel jet are hypothesized as the physical mechanisms that explain the overall emission behavior.