Has to be repositioned after each night of slumber. Love the mattress itself, but the mattress protector is another story. Since Tempur-Pedic advertises sheets and protectors designed specially for their mattresses, I was expecting better. We have the same problem with high quality (thread count) sheets, which are not Tempur-Pedic products. Due to this, I am reluctant to buy Tempur-Pedic sheets, because of the poor fit of the mattress protector. I do not want to purchase Tempur-Pedic pricy sheets, which fit and stay in place no better than what I have already.