Evidence is emerging that IBS, a hitherto enigmatic disorder thought to be predominantly related to psychological factors, has a microorganic basis in a subset of patients with the disease. Post-infectious IBS (PI-IBS), commonly of the diarrhoea-predominant subtype (defined as new development of IBS following acute infectious diarrhoea), is one such condition known to occur in up to 10–30% individuals after acute gastroenteritis. However, following acute infectious gastroenteritis, patients can also develop post-infectious malabsorption syndrome (PI-MAS), popularly known as tropical sprue. As no study on PI-IBS has rigorously excluded tropical sprue by appropriate investigations, including small intestinal biopsy, the frequency of tropical sprue among patients with PI-IBS is not known. Small intestinal bacterial overgrowth (SIBO) has been suggested to be associated with IBS in general, and in particular diarrhoea-predominant IBS, including PI-IBS. SIBO is also known to be associated with tropical sprue. As both IBS, particularly the subset probably associated with SIBO, and tropical sprue improve with antibiotic treatment, we provide evidence and an explanatory model to support a link among these disorders.