Crohn's disease (CD) is a chronic inflammatory bowel disorder of unknown etiology. An involvement of the intestinal lymphatic system has been suggested. Recently, monoclonal antibodies have become available to distinguish lymphatic vessels from blood vessels. The aim of the study was to examine the distribution of lymphatic vessels in ileal and colic walls of patients affected by CD and compare it with healthy controls and other inflammatory bowel diseases. Twenty-eight cases of CD, 13 cases of other inflammatory bowel diseases, and 10 normal ileal and colic walls were studied. Immunohistochemical staining was performed using the monoclonal antibody D2-40. Quantification of lymphatic vessels was performed by identifying four fields with high density of lymphatics and then counting the number of lymphatic vessels at high resolution. Lymphatic diameter was also evaluated by using an ocular micrometer. Lymphatic vessels showed the highest density in CD specimens. The median number of lymphatics was significantly higher both in ileal and colic samples of CD than the other inflammatory diseases as well as normal controls. Moreover, in patients with CD, diffuse lymphangiectasia was also observed. The present data suggest that lymphangiogenesis and lymphangiectasia probably play a role in the pathogenesis of CD.