Healthy gut microbiota performs many important functions and is necessary for maintaining the body in a state of metabolic equilibrium. Unfavourable conditions may lead to the development of small intestinal bacterial overgrowth (SIBO), a condition defined as an excessive bacterial colonisation of the small intestine. The prevalence of SIBO in the general population is still unknown. Some risk factors which have been implicated in the pathogenesis of SIBO include disorders of gastrointestinal motility, history of intestinal resection, chronic comorbidities, and elderly age. SIBO may present with a range of non-specific symptoms, the most common of which are bloating and abdominal distension, nausea, abdominal pain, bowel movement disorders, lack of appetite or unintentional weight loss. SIBO is diagnosed by invasive tests and the increasingly popular non-invasive breath tests. Supplementary diagnostic examinations include microscopic evaluation of stool for the presence of fat, complete blood count, and measurement of vitamin B12 or albumin levels. First-line treatment is based on eubiotics, one of which is rifaximin-α. The drug is characterised by a broad spectrum of activity against a variety of Gram-negative and Grampositive bacteria, both aerobic and anaerobic. A major component of SIBO therapy is appropriate diet combined with lifestyle modifications (regular physical activity, avoidance of stress, and restoration of normal sleep pattern). In rare cases, for example in patients with anatomical anomalies, surgical management should be considered. The paper presents basic information about SIBO, which is useful in the everyday practice of primary care physicians.