In order to meet future emissions standards, diesel engines may require the use of exhaust gas recirculation (EGR). The NOx-bsfc trade-off can be improved by using an exhaust-to-engine coolant heat exchanger. If care is not taken, the durability of the cooler may be compromised by sulfuric acid condensation from the exhaust gas. This paper presents a computer model for predicting the dew-point, acid condensation rate, and condensate composition inside an EGR cooler. Effects of fuel sulfur content, pass arrangement, surface fouling, coolant temperature, and engine operating point on acid condensation were identified by applying the model to a prototype heat exchanger.