A fitted bed sheet includes a substantially rectangular main body portion of substantially the same dimensions as a selected mattress. Side portions extend from the sides of the main body portion and terminate in longitudinal edges. End portions extend from the ends of the main body portion and terminate in end edges. Substantially vertical corner seams join the side portions to the adjacent end portions, each seam extending from an inner end at a corner of said main body portion to an outer end at the junction of a longitudinal edge and an end edge. The side edges and end edges are thereby joined together to define a perimeter. There is elastic in at least a portion of the perimeter, to permit the sheet to fit snuggly around a mattress. The present invention is particularly characterized in that the vertical corner seams are at least partly elasticized.