The production of small quantities of monoclonal antibodies and recombinant proteins was carried out using a new low cost production system, the Super Spinner. Into a 1 1 standard Duran(R) flask a membrane stirrer equipped with a polypropylene hollow fiber membrane was installed to improve the oxygen supply by bubble-free aeration. The aeration was facilitated by using the CO2 conditioned incubator gas, which was pumped through the membrane stirrer via a small membrane pump. The maximal oxygen transfer rate (OTR(max)) of the Super Spinner was detected. For this purpose one spinner flask was equipped with an oxygen electrode. The OTR(max) was measured by the dynamic method. The ratio of membrane length to culture volume was adapted corresponding to the oxygen uptake rate of the cells according to the desired cell density. A balanced nutrient supply resulted in an optimal formation and yield of products.