I am new to both game programming and XNA, so I apologize if I'm missing a simple concept or something. I have created a simple 3D game with a player and a crate and I'm working on getting my collision detection working properly. Right now I am using a BoundingSphere for my player, and a BoundingBox for the crate. For some reason, XNA only detects a collision when my player's sphere touches the front face of the crate. I'm rendering all the BoundingSpheres and BoundingBoxes as wire frames so I can see what's going on, and everything visually appears to be correct, but I can't figure out this behavior. I have tried these checks: playerSphere.Intersects(crate.getBoundingBox()) playerSphere.Contains(crate.getBoundingBox(), ContainmentType.Intersects) playerSphere.Contains(crate.getBoundingBox()) != ContainmentType.Disjoint But they all seem to produce the same behavior (in other words, they are only true when I hit the front face of the crate). The interesting thing is that when I use a BoundingSphere for my crate the collision is detected as I would expect, but of course this makes the edges less accurate. Any thoughts or ideas? Have I missed something about how BoundingSpheres and BoundingBoxes compute their intersections? I'd be happy to post more code or screenshots to clarify if needed. Thanks!