A simulation model of the glucose-insulin system in the postprandial state can be useful for studying the pathophysiology of diabetes. Here we present a new simulation model which describes the physiological events which occur after a meal, by employing the quantitative knowledge which has become available in recent years. Model parameters were set to fit data of 204 normal subjects which underwent a triple tracer meal protocol which provided quasi model-independent estimates of major glucose and insulin fluxes. Model results are shown in describing normal daily life (breakfast, lunch, dinner) both in normal and pathophysiological situations. The potential of the model for studying type 1 diabetes is illustrated by simulating both open- and closed-loop insulin infusion strategies.