It is surprising that in the gastrointestinal tract, with a primary barrier function and a large population of immunocytes, a major role for immunological damage has been convincingly established only for a few diseases; pernicious anaemia, gluten-sensitive enteropathy and GVHD. The complexities in investigating this relatively inaccessible area and the necessity for studying appropriate controls by similar techniques are some of the reasons that explain this paucity of data. Tropical sprue is a syndrome with an unusual geographical distribution and unknown aetiology. Alterations in gut immunocytes, especially EL, in this disease suggest that immune-mediated mechanisms may be important in the pathogenesis. However, the available data suggests that the initiating event leading to persistent damage to enterocytes in the stem cell compartment is unlikely to be immune mediated and that the immunological alterations are secondary to the loss of barrier function consequent to enterocyte damage.