Nitrogen compounds present in crude sources constitute serious problems both for producers and consumers. For producers, these compounds are responsible for poisoning catalysts during the refining processes. For consumers, these compounds are responsible for the degradation observed in fuels during storage and handling. The quality of petroleum, as measured by degrees API gravity, continues to decrease in quality. This, coupled with the inevitable use of other crude sources, if used in quantity will further decrease the stability of middle distillate fuels. In this article we present our method for the separation and quantitation of the slate of nitrogen compounds present in middle distillate fuels derived from petroleum, oil shale and tar sand sources. Results from our laboratory indicate that of all of the nitrogen compounds present in middle distillate fuels, the indole type structure is the most deleterious.