I ordered a size 8 which was snug even with a thin sock, but returned for an 8.5 so that I could wear a bulkier winter sock.  This is a warm boot, comfortable, and I am very happy with it.  However it is not a thicker insulated boot, so if you have severe winters in your area (or spend a lot of time outdoors) you may want to try something with a little more bulk.  Love Columbia's Omni-heat technology, and have several garments that use it.