We describe a 53-year-old man with a history of diarrhea temporally related to the use of flutamide. He developed an acute abdomen, and presented with an ileocecal intussusception due to an edematous ischemic cecum. The ischemia was due to enterocolic lymphocytic phlebitis (ELP), with numerous associated thrombi. The phlebitis involved not only the ischemic area but also the grossly unaffected areas, including the entire right colon, terminal ileum, and appendix. All layers of the bowel wall were involved. Mesenteric veins were also prominently affected, but the arteries were spared. This rare form of vasculitis was associated with a marked lymphocytic infiltrate involving the epithelium of the entire right colon, ileum, and appendix. This is the first reported case of ELP occurring in conjunction with lymphocytic colitis, lymphocytic enteritis, and lymphocytic appendicitis. The temporal association of the patient's symptoms with flutamide use suggests that this peculiar form of lymphocytic inflammation of the veins and mucosa likely represents a drug reaction. We suggest that some cases of lymphocytic colitis may also be associated with ELP but are unlikely to be recognized unless affected submucosal vessels happen to be included in the biopsy.