A review with 55 refs. Oxygen is a key substrate in animal cell metab. It has been reported that the oxygen uptake rate (OUR) is a good indicator of cellular activity, and even under some conditions, a good indicator of the no. of viable cells. The measurement of OUR is difficult due to many different reasons. In particular, the very low specific consumption rate (0.2*10-12 mol cell h-1), the sensitivity of the cells to variations in dissolved oxygen concn. and the difficulty to provide oxygen without damaging the cells are problems which must be taken into account for the development of OUR measurement methods. Different solns. based on an oxygen balance on either the liq. phase or around the entire reactor, and with a variable or stable concn. of dissolved oxygen have been reported. The accuracy of the OUR measurements and the required anal. devices are very different from method to method. [on SciFinder (R)]