Abstract: An agitator mill includes a housing having first and second ends defining a milling chamber adapted to hold a grinding media therein. The housing includes an inlet to introduce product into the milling chamber to be ground and an outlet for the discharge of the ground product. An agitator shaft includes a first end rotatably supported on the first end of the milling chamber, a plurality of spaced agitation elements thereon and a second free end. A freely rotatable screen device is supported on the second end of the housing at the outlet and has a leading end which extends to proximate the second end of the agitator shaft. The ground product flows through the screen device out of the outlet, with the screen device being caused to rotate by the fluid coupling of the agitator shaft with the screen device.