At Boliden Mineral＇s Aitik concentrator approx 16 Mtpy is milled in five parallell fully autogenous grinding circuits. The original maximum throughput control strategy lead to overruns of the primary mills. Tests showed peak throughput at mill power lower than max power. The peak power varies due to variable ore grindability implying a need for continuous adjustment of the millpower setpoint. The main control functions are mill power setpoint optimization and ore feed control. The power optimization loop finds the optimum power setpoint, related to the ore grindability, giving the highest possible throughput. The control system has improved the milling capacity by approx, 5%.