Since the discovery in 1987 that it relaxes vascular smooth muscle, nitric oxide has emerged as an important inhibitory nonadrenergic noncholinergic neurotransmitter throughout the gastrointestinal tract. Immunohistochemical demonstration of its presence and its role in peristalsis, colonic relaxation, and sphincter function are discussed. Intestinal pseudoobstruction poses difficult diagnostic and management problems. However, new primary pathologies causing chronic disease are being identified and pharmacologic treatment of acute disease may be helpful. The repeatability and value of visceral evoked potentials in anorectal disease is discussed. Long-term data about the clinical spectrum of Hirschsprung's disease and immunohistochemical means of diagnosis are reviewed. An update is provided on the etiology and complications of severe constipation. Other areas reviewed include diarrhea and fat excretion, new motility pharmacotherapies, food and colonic motility, and optimum methods for measurement of colonic transit.