Tuberculosis has a dramatic effect on nutritional state and this has been borne out in all the studies that have investigated body composition in affected patients. I have included some of the key studies in this review; those I have not cited generally reach the same conclusions. Such malnutrition undoubtedly contributes to the morbidity of the disease and may also contribute to mortality, particularly in resource-poor settings where nutritional state, even in the "healthy," may be parlous. The extent to which such malnutrition also contributes to pathology remains unclear. Certainly, in other models, nutritional depletion has a major impact on immune function (Chandra, 1997) and depression of lymphocyte function cannot be a desirable commodity in an individual fighting invasive mycobacterial infection. Considering the reverse relationship, there is good evidence, both at the population level and at the clinical level, for the effect of primary malnutrition on tuberculosis, both to increase frequency of occurrence and to exacerbate clinical manifestations. It has not been possible to explore this relationship within the context of this paper but it is clearly an important aspect of the bi-directional relationship between tuberculosis and malnutrition. There is still more to be understood about the pathophysiology of the wasting seen in chronic infections such as tuberculosis but it is clear that, in addition to good anti-tuberculous therapy, such patients need a good supply of nutrition during the treatment/recovery phase. In the developed world, this may include medical measures to achieve nutritional support whereas in resource-poor settings, nutritional intake may have more to do with equitable resource distribution and community involvement in health care.