SIBO (small intestinal bacterial overgrowth) is defined by bacterial overgrowth or colonization of the small intestine in combination with gastrointestinal symptoms such as bloating, nausea, pain, diarrhoea, malabsorption and food intolerance. SIBO can be caused by various mechanisms such as reduced intestinal motility, altered gastrointestinal anatomy, reduced gastric acid or pancreatic enzyme production, altered bile acid metabolism, or immune defects. Accordingly, SIBO often develops secondary to different underlying diseases.Diet has a fundamental influence on the composition of the intestinal microbiome and is therefore also a potential pathomechanism in SIBO. Furthermore, food intolerances are common in SIBO patients. However, both aspects have so far been insufficiently investigated. Nevertheless, elemental diets, carbohydrate-reduced diets, as well as pre- and probiotics are potential therapy options.This article provides a summary of current knowledge on the pathophysiology, diagnosis and treatment of SIBO, with particular emphasis on the role of nutrition and the microbiome.