The study of nitrogen (N) species released during oil shale processing is an important research area because both oil shale and shale oil are rich in N. Combustion of N-bearing fuels can produce nitrogen oxides (NOx). The emissions of NOx are limited by law due to environmental concerns. Ammonia is a major N by-product in oil shale processing. Figure 1 shows the distribution of N in different product streams in our LLNL gravity-bed recycle retort system. The retort water and pyrolysis gases carry 4% and 0.2% of the total N, respectively, and ammonia accounts for most of the N in these product streams. Ammonia also accounts for half of N in the combustion gas stream, and NOx for the other half. The concentrations of HCN and molecular nitrogen (N2) in the combustion gas stream were not determined, so they were not included in the balance. The total N balance is poor, probably due to species not measured and to the lack of accuracy in determination of the N content in solids. We studied ammonia evolution by pyrolyzing oil shale under a given time-temperature history and measuring the total yield of ammonia by an ammonia electrode.1 We learned that: the NH3 yield increased rapidly as the final pyrolysis temperature increased above 500°C; NHg evolved at oil-generating temperatures came from organic N, while the high temperature NH3 was from both organic and inorganic sources; the yield at T > 500 °C is affected by the decomposition reaction; and steam worked as an inhibitor for NH3 decomposition. Earlier, we reported an on-line technique measuring real-time evolution of ammonia using a mass spectrometer.1,2 In this paper, we summarize the on-line ammonia evolution rates for two Green River Formation oil shales and one Eastern oil shale under inert gas (argon) and also under steam. We analyze the contribution of the organic/inorganic sources of N to the NH3 yield at different pyrolysis temperatures and show oil shale N-chemistry during pyrolysis. We also compare the kinetics of ammonia evolution with that of other pyrolysis gases.