Stabilization of the unstable regime of a flow reactor with distributed parameters is considered. The stabilizing system relates the rate of supply of material to the reactor to the deviation of the output concentration from the steady-state value. An isothermal autocatalytic reaction is chosen as the simplest reaction for which nonuniqueness of the steady-state regimes is possible. It has been found [3] that there are three possible steady-state regimes. Their stability was investigated in [8]. It has been shown that the middle regime is unstable, only the first mode of the small disturbances being unstable over a broad range of the parameters.