Sixty-three consecutive reexcisions of bowel for recurrent Crohn's disease where the former excision had removed all apparent disease were studied. Nine pathologic parameters (small ulcers, granulomas, regeneration, metaplasia, submucosal lymphoid follicles, transmural inflammation, large ulcers, sinuses, and strictures) were correlated to the interval of time since the former excision to document the disease progression. By regression analysis, only the presence of strictures or large ulcers correlated with time. First quartile times suggest that small ulcers and granulomas were the earliest lesions of those studied. Regeneration, metaplasia, submucosal lymphoid follicles, and transmural inflammation appear to be sequelae of ulceration. Sinuses and strictures are late complications of ulceration. The results confirm clinical, radiological, and subjective pathological impressions of the progress of the disease and suggest a central role for ulceration in this disease.