This chapter reviews the assessment and management of non-irritable bowel syndrome (IBS) functional bowel disorders (FBDs) – functional bloating, functional constipation and functional diarrhoea. The Rome IV criteria highlight differences between functional abdominal bloating, a subjective assessment, and functional abdominal distension, an objective measure. Functional diarrhoea is defined as the passage of loose or watery stools. Unspecified functional bowel disorder is defined as patients who have no organic pathology but fail to meet diagnostic criteria for any of other functional bowel disorders. Opioid-induced constipation (OIC) is a change in bowel frequency, worsening straining, a feeling of incomplete bowel emptying or distress associated with bowel habits upon initiation of opioids. Patients with FBDs can become dissatisfied by the way information is communicated and provided, making effective communication paramount in helping to address patient concerns. Somatization symptoms can also be present in these patients, which are often extra-colonic in nature, such as headaches, dysuria, back pain, palpitations and muscle aches.