We have determined the outcome of a defined policy for the management of distal ileal Crohn's disease using a prospective computer-based analysis of 139 patients diagnosed between 1970 and 1988 with a mean follow-up of 10 years. The policy in outline consists of conservative treatment for acute obstructive episodes, resection or strictureplasty for recurrent obstructive episodes, surgical treatment for abscess and fistula formation and specific medical treatment (corticosteroids, immunosuppressive therapy or metronidazole) for symptomatic non-obstructive disease. Twenty-nine patients had a benign course without resection. The remainder were treated surgically at some time but only 28 of these patients had specific treatment before operation. Thirty-three needed more than one resection and five needed more than three surgical procedures. Immediate, early or delayed surgical treatment did not affect the reoperation rates or the long-term outcome. Eleven patients died, ten of causes unrelated to Crohn's disease. Of the 128 living patients, 114 are fit and well, and only two are currently taking specific medication. Fourteen are unwell of whom six either need or have refused further surgery which could restore them to good health. This management policy has achieved excellent long-term results in nearly all patients, and our findings suggest that the timing of surgery and its nature are more important in determining outcome than specific medical therapy.