The etiology of hemorrhoids has been explained in the past based on anatomic principles, but this study examines the relationship of resting anal pressures to hemorrhoid etiology in 38 patients with hemorrhoids and 29 controls with no perianal symptoms. Three months after treatment by elastic band ligation, anal pressures were again measured in the hemorrhoid group. Anal pressures were significantly higher in the hemorrhoid group before treatment (102 +/- 26.33 mmHg) as compared with the controls (76.75 +/- 19.56 mmHg) (P less than .001). Three months following elastic band ligation there was a small drop in anal pressure (100 +/- 26.84 mmHg) but it remained significantly higher than the control group. There was also a significant correlation between symptoms and level of anal pressures. The results indicate that persons with hemorrhoids have higher anal pressures than controls. Elastic band ligation relieves the symptoms but should not affect the anal sphincter pressure. The fact that the anal pressures remained high after treatment could imply that higher pressures are an etiologic component in the formation of hemorrhoids.