Agitator ball mill - having a horizontally arranged grinding vessel -- which encloses a cylindrical grinding chamber bounded by a wall of the grinding vessel and by a grinding chamber inner boundary, -- with a grinding material feed leading in into the grinding chamber at one end, and -- with a grinding material outlet leading out of the grinding chamber at the other end, having a grinding material/grinding bodies separating device arranged upstream thereof, - having an agitator arranged in the grinding chamber, that has -- a rotatably driveable agitating shaft having a central longitudinal axis and -- agitating discs mounted to the agitating shaft in a manner fixed against rotation relative thereto and spaced by a distance (a) from one another, --- wherein two adjacently arranged agitating discs are bounding a grinding cell, respectivly, --- wherein the agitating discs comprise openings connecting adjacent grinding cells, and --- wherein - with respect to the central longitudinal axis - the agitating discs have a radial extension R18 from the grinding chamber inner boundary to the radially outer edge of the agitating discs, characeterized in that the openings are embodied as grinding material passage openings and are arranged only in the immediate proximity of the grinding chamber inner boundary, wherein the grinding material passage openings have a radially outer boundary, respectively, that has a distance R28 from the grinding chamber inner boundary in radial direction of the agitating disc, wherein for the ratio of the distance R28 of the radially outer boundary of the grinding material passage openings to the radial extension R18 of the agitating discs the following condition applies: 0.05. R18 ≤ R28 ≤ 0.25 · R18, and in that the agitating discs are otherwise closed. - having a horizontally arranged grinding vessel -- which encloses a cylindrical grinding chamber bounded by a wall of the grinding vessel and by a grinding chamber inner boundary, -- with a grinding material feed leading in into the grinding chamber at one end, and -- with a grinding material outlet leading out of the grinding chamber at the other end, having a grinding material/grinding bodies separating device arranged upstream thereof, -- which encloses a cylindrical grinding chamber bounded by a wall of the grinding vessel and by a grinding chamber inner boundary, -- with a grinding material feed leading in into the grinding chamber at one end, and -- with a grinding material outlet leading out of the grinding chamber at the other end, having a grinding material/grinding bodies separating device arranged upstream thereof, - having an agitator arranged in the grinding chamber, that has -- a rotatably driveable agitating shaft having a central longitudinal axis and -- agitating discs mounted to the agitating shaft in a manner fixed against rotation relative thereto and spaced by a distance (a) from one another, --- wherein two adjacently arranged agitating discs are bounding a grinding cell, respectivly, --- wherein the agitating discs comprise openings connecting adjacent grinding cells, and --- wherein - with respect to the central longitudinal axis - the agitating discs have a radial extension R18 from the grinding chamber inner boundary to the radially outer edge of the agitating discs, -- a rotatably driveable agitating shaft having a central longitudinal axis and -- agitating discs mounted to the agitating shaft in a manner fixed against rotation relative thereto and spaced by a distance (a) from one another, --- wherein two adjacently arranged agitating discs are bounding a grinding cell, respectivly, --- wherein the agitating discs comprise openings connecting adjacent grinding cells, and --- wherein - with respect to the central longitudinal axis - the agitating discs have a radial extension R18 from the grinding chamber inner boundary to the radially outer edge of the agitating discs, --- wherein two adjacently arranged agitating discs are bounding a grinding cell, respectivly, --- wherein the agitating discs comprise openings connecting adjacent grinding cells, and --- wherein - with respect to the central longitudinal axis - the agitating discs have a radial extension R18 from the grinding chamber inner boundary to the radially outer edge of the agitating discs,