The classical example of an integrating process with inverse response is level control of a boiler steam drum. The "boiler swell" problem can lead to a transfer function between the drum level and boiler feedwater flow rate that contains a pure integrator and a positive zero, in addition to some deadtime and lags. This paper presents a procedure for identifying the transfer-function parameters for this type of system from step response data. A proportional-integral controller tuning procedure is also presented. Because the process contains an integrator and the proportional-integral controller also contains an integrator, controller tuning is somewhat complex. The proposed method determines the smallest possible value for integral time. Then, using this value, the controller gain that gives a +2 dB maximum closed-loop log modulus is calculated. Simple Matlab programs are given for performing these calculations. The use of proportional-integral-derivative control is also briefly studied, but the typically noisy level signals preclude the use of derivative action.