The clinical features and the long-term results of surgery for anal fistula were studied. Fistula distribution was subcutaneous (13%), intermuscular (14%), low anal (55%) or high anal (18%). There were no pelvirectal fistulas. The location was mostly posteriorly in the anus, except for the low anal fistulas, which were most frequent anteriorly. Follow-up examination was carried out on 199 patients, on average 9 years after fistula operation. The recurrence rate was 11% after laying open of fistula, with the highest rate (26%) in high anal fistula. The most common causes of recurrence were undetected internal opening and incomplete laying open of the fistulous tract proper. Most (91%) of the recurrences appeared within 18 months after surgery. Minor defects in anal control were found in 34% of the patients, and in 9% of controls matched for age and sex but with no anal surgery. Multiple operations for anal fistula, and also a gutter-shaped and a firm or hard scar in the anal canal adversely affected anal control. The amount of divided sphincter musculature did not influence the incidence of postoperative anal incontinence.