A kinetic model of overflow metabolism in Saccharomyces cerevisiae was used for simulation of aerobic fed‐batch cultivations. An inhibitory effect of ethanol on the maximum respiration of the yeast was observed in the experiments and included in the model. The model predicts respiration, biomass, and ethanol formation and the subsequent ethanol consumption, and was experimentally validated in fed‐batch cultivations. Oscillating sugar feed with resulting oscillating carbon dioxide production did not influence the maximum respiration rate, which indicates that the pyruvate dehydrogenase complex is not involved as a bottleneck causing aerobic ethanol formation. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 474–482, 1998.