Orthopedic physicians often recommend that patients sleep on firm mattresses to alleviate low-back pain, but a study in last week's issue of the Lancet suggests that such advice is based on little more than folklore. In a randomized trial, researchers at the Kovacs Foundation in Spain assigned 313 subjects with chronic low-back pain to either a firm or a medium-firm mattress to sleep on for three months. Good news for those of us who like a little give in our cribs: patients who slept on the medium-firm mattresses were twice as likely as those sleeping on firm ones to report reduced pain while lying in bed or getting up in the morning. They also had less disability associated with back pain and were less reliant on pain-killing drugs. --S.S.