In this paper, results from an experimental and computational study relating NO and soot emissions in a Diesel engine to heat release rate characteristics are reported. The experiments were carried out in a Cummins N-14 single-cylinder Diesel engine. The computations were carried out for the same engine. It is shown that, more than any significant feature of the heat release rate itself, the NO appears to be related to the temperature of the reactants with higher temperatures resulting in higher NO emissions. Relationships of NO to the heat release rates are secondary to this primary dependence. In general, the soot-NO trade-off relationships appear to hold. However, for the range of conditions studied, soot and NO are found to simultaneously decrease with decreasing air temperatures. It is also found that at the most retarded timings, NO and soot simultaneously decrease but with a severe penalty in fuel consumption. Also, for the range of conditions studied, the soot exhaust emissions appear to be correlated with its spatial distribution in the chamber.