This paper describes a study which was conducted to simultaneously optimize several diesel engine design and operating parameters for low exhaust emissions using the Taguchi method. A single cylinder, research, diesel engine equipped with a high pressure, cam-driven, electronic unit injector was used in this optimization experiment. The major effects of key engine design parameters on exhaust emissions were quantified and optimum parameter settings were determined. Measurement of exhaust emissions using the optimum parameter settings showed that particulates and NOx emissions were significantly lower than those obtained for the baseline engine. The Taguchi method was found to be a useful technique for the simultaneous optimization of several engine parameters and for predicting the effect of various design parameters on diesel exhaust emissions.