Small bowel bacterial overgrowth is a syndrome caused by an abnormal number of bacteria in the upper part of the small bowel and associated with a complex array of clinical symptoms, i. e., chronic diarrhoea, steatorrhoea, macrocytic anaemia, weight loss, and less commonly, protein-losing enteropathy. The most common underlying factors are small intestinal stagnation or dysmotility, intestinal obstruction, blind or afferent loops, and decreased gastric secretion. The treatment usually consists in the eradication of bacterial overgrowth with repeated courses of antimicrobials, correction of associated nutritional deficiencies and, when possible, correction of the underlying predisposing conditions.