Abstract: Crowd simulation is typically an expensive task. We introduce a level of detail system, useful for varied animated crowds, capable of handling several thousands of different animated characters at interactive frame rates. This is accomplished using two complementary structures to reduce memory consumption and optimize the rendering stage. The first structure is a skeleton, with associated octrees per limb, that is used for computing level of detail of geometry and animation. The second structure is a tiling of the scene that is used to select the character's level of detail for geometry, animation and behavior. A quadtree is built on top of this tiling and used for further rendering optimization, allowing us to combine geometry from different characters in parts of the scene that are far away from the camera. The system outperforms similar methods in memory requirements and/or complexity and is capable of rendering crowds composed of a quarter million characters.