A somewhat paradoxic aspect of childbirth is the association of this physiologic process with acute pain. The experience of pain during labor is the result of complex processing of multiple physiologic and psychosocial factors on a woman's individual interpretation of nociceptive labor stimuli. The nature of labor pain, particularly its physiologic and psychologic influences, is reviewed in the context of a multidimensional framework of the pain experience and an understanding of the origin of labor pain stimuli, of potential adverse effects of the pain response, and of the concepts of suffering and comfort. (Am J Obstet Gynecol 2002;186:S16-24.)