AbstractA perifusion system was designed in order to study glucose and glutamine metabolism by freshly harvested Ehrlich ascites tumour cells in steady state conditions. Cells were perifused in the presence of 5 mMglucose, 0·5 mMglutamine or 5mMglucose and 0·5 mMglutamine. The results in steady state reveal that both substrates glucose and glutamine are continuously wasted by tumour cells, excreting two moles of lactate per mol of glucose and one mol of glutamate and ammonia per mol of glutamine consumed into the medium. Glutamine consumption in the presence of glucose was higher than with glutamine alon