To the Editor.— How often have you heard from your patients or friends with a chronic "low back problem": "No matter how firm a surface I sleep on, at times it is impossible to find a comfortable position," or "I wake up with a low back ache even if I sleep on a hard surface or sleep with my hips and knees slightly flexed." I was recently in such a condition myself and happened to be living in a house that uses hammocks as extra beds. One night, after everything else had failed, I decided to try a hammock and, for the first time in weeks, slept comfortably and woke up free of low back ache. I have continued to sleep in a hammock for six months now, and it continues to be more comfortable for my back than a hard bed. As a long-term sufferer, I have read much