Abstract: The present invention encompasses a mattress (20) for a variable width bed. The mattress (20) has a top section (40) positioned on a base section (50, 60) with the top section (40) having a width greater than the width of the base section (50, 60), so that wing portions of the top section (40) extend beyond the sides of the base section (50, 60). The top section (40) may also have a pair of relief notches (140) defined therein with one relief notch (140) positioned generally above each side of the base section (50, 60). The mattress (20) cooperates with one or more expansion members (30) that are sized so that when placed at the side of the base section (50, 60) and below the wing portion of the top section (40) the sleeping surface of the mattress (20) will be substantially flat and substantially seam and crease free.