A prospective study was carried out on the anorectal function in patients with hemorrhoids (group H, n = 25) versus normal controls (group T, n = 22) and on the effect at three months of hemorrhoidectomy on sphincter function and anal continence. Hemorrhoidectomy was performed by the same surgeon using the standard Milligan Morgan procedure in all cases. All patients and controls underwent an anal manometry, a measure of the length of the anal sphincter and a saline continence test. Anal resting pressure was higher in group H as compared to group T before hemorrhoidectomy (136 +/- 32 cm H2O vs 98 +/- 19 p less than 0.001). After hemorrhoidectomy, and resting pressure was significantly lower (141 +/- 21 cm H2O vs 106 +/- 25 p less than 0.01). Anal length was similar in group H and in group T (50.2 +/- 6.6 mm vs 45 +/- 5.5 NS) but decreased significantly after hemorrhoidectomy (41.9 +/- 7.6 vs 50.3 +/- 7.3 p less than 0.01). Ultraslow waves were more often observed in patients with piles (60 p. 100 vs 9 p. 100 of normal controls). After hemorrhoidectomy ultraslow waves were less commonly encountered (25 p. 100 p less than 0.05). Anal leakage during the saline continence test was observed in 12 and 82 p. 100 of patients before and after hemorrhoidectomy, respectively (p less than 0.001). No anal leakage was observed in the control groups. After hemorrhoidectomy the mean volume of anal leakage was of 190 ml. In 35 p. 100 of the patients, anal leakage occurred before the anal infusion of 500 ml.(ABSTRACT TRUNCATED AT 250 WORDS)