Sixty-seven patients with Crohn's disease undergoing 81 resections followed by a restorative procedure were reviewed to evaluate the influence of microscopic disease at the margin of resection on the recurrence rate. The average follow-up after resection was 5.6 +/- 2.8 years. The resectional margins were classified into three groups depending on the microscopic appearance of the most involved margin. Recurrent disease developed in 36 per cent of the resections without microscopic evidence of Crohn's disease, while 38 per cent of the resections with signs of Crohn's disease developed a clinical recurrence. The recurrence rate increased with the follow-up time, but was independent of microscopical disease at the resectional margins. Therefore we recommend restricted resection of macroscopically diseased bowel. Microscopical involvement does not seem to increase the recurrence rate.