This U.S. Bureau of Mines paper verifies a technique for mapping the exhaust emission levels of a diesel engine during transient operation. Particulate matter, oxides of nitrogen, hydrocarbons, and carbon monoxide emissions were sampled for discrete segments of various transient cycles. Each cycle consisted of four distinct segments. The discrete segments are described by average engine conditions, rate of change variables, and segment length. Regression analysis was used to develop equations relating the emission levels during each segment to the engine parameters. The regression equations were then used to obtain estimates of composite emission levels of several complex transient cycles that were subsequently tested. These cycles included the Environmental Protection Agency (EPA) heavy-duty transient cycle and two simulated heavy-duty cycles developed for underground mine vehicles. Comparison of the predicted and measured cycle emissions are made for the EPA heavy-duty cycle and the simulated mine cycles. Good agreement was obtained between the predicted and measured emission levels.