Lymph node lesions attributable to ischaemia are described in the mesenteric nodes from 10 patients with volvulus of the small and large bowel. Frank infarction, the microanatomy of which differs from that seen in superficial lymph nodes, is one of the nodal lesions evoked by ischaemia. Two others in the form of lymphocyte depletion and capsular hypervascularity also appear to result from vascular occlusion. These three lesions were also found in nodes associated with 'primary' venous and arterial infarction of the bowel mucosa, but not in non-vascular diseases of the small bowel or colon. The enhanced frequency of infarction in volvulus with mucosal necrosis, as opposed to cases with 'primary' vascular thromboses suggest that ischaemic lymph node changes are more frequent when several sets of vessels are occluded. Distension of lymph node sinuses, erythrocyte extravasation, and dilatation of small intranodal vessels were not restricted to vascular cases, and appear to be less specific reactions to ischaemia. The range of ischaemia-induced reactions is wider than has hitherto been recognized in human lymph nodes.