Using health statistics from the United States and England and Wales, we review the epidemiology of constipation and possible etiologies of this disorder as suggested by its epidemiologic distribution. The analysis revealed that constipation is one of the most common chronic digestive disorders in the United States, affecting one of every 50 people. The occurrence of constipation increased with advancing age, showing an exponential increase in prevalence after the age of 65. The age distribution of constipation was similar in both sexes, but overall constipation was three times more common in women than in men. Constipation more frequently affected nonwhites than whites, and people from families with low income or less formal education. The characteristic epidemiologic pattern of constipation suggests the influence of environmental factors. Insufficient dietary fiber is widely believed to be a major cause of constipation, yet it is difficult to devise a mechanism by which dietary fiber alone could produce the marked differences observed between gender, race, and socioeconomic status. Recent evidence suggests that disruption of neural regulation of colonic motility plays an important role in the development of chronic constipation. This loss of neural regulation may result from mechanical damage to the pelvic nerves due to childbirth or pelvic surgery, exposure to environmental toxins (e.g., organochlorine insecticides or heavy metals), or possibly exposure to an infectious agent. Other environmental factors that may play a role in the pathogenesis of chronic constipation have not yet been elucidated. Consequently, studies examining the epidemiology of chronic constipation are important for providing insight into potential environmental risk factors relevant to the etiology of this disorder.