In a prospective study of liver function in 19 patients with Crohn's disease, examination of liver biopsies showed a sinusoidal dilatation in 16 patients. This dilatation was moderate in 5 cases and pronounced in 6 cases and was associated with a closely parallel dilatation of the centrilobular vein. There was no correlation between these diffuse vascular changes and the site of the bowel disease, the clinical presentation, and the course of the disease. The pathogenesis of this sinusoidal dilatation is unknown.