A simple feeding method for controlling specific growth rate in fed-batch culture was developed. This method applies a constant feed rate using a concentrate reservoir and two mixing chambers in series to simulate the exponential feeding. Fed-batch cultures with Escherichia coli showed that the present feeding method could sustain the cells growing at predetermined specific growth rates, where the time length for exponential growth was dependent on the magnitude of the growth rate. The present feeding method is convenient to operate, requires no computerized control equipments, and thus could expect an extensive application in fed-batch culture. (C) 2002 Elsevier Science B.V. All rights reserved.