The role of the anorectal band in the genesis of hemorrhoids is studied. The anorectal band is a fibroepithelial tube which is a remnant of the anorectal sinus. Seventy-six hemorrhoid patients and 32 controls were studied. Rectal neck pressure recording was done for all subjects. Two biopsies were taken from the lower rectal neck of each individual of the hemorrhoid and the control group, and were examined microscopically. Rectal neck pressure was measured in 67 patients of the hemorrhoid group after internal sphincterotomy. The mean rectal neck pressure in the hemorrhoid patients was significantly higher than the controls. Post-operative pressure measurement showed normal values. Microscopic examination of the rectal neck specimens revealed the presence of fibrous bands in the lower rectal neck submucosa of all hemorrhoid patients and in only one control subject. Evidence suggests that this fibrous band is the anorectal band which is an embryonic vestige. A new theory of the pathogenesis of hemorrhoids is presented. Evidence in support of the theory is also shown. The treatment of hemorrhoids in view of this theory is discussed.