This guideline covers diagnosing and managing irritable bowel syndrome (IBS) in people aged 18 and over. It details how to accurately diagnose IBS, and aims to improve the quality of life for adults with IBS by promoting effective management using dietary and lifestyle advice, pharmacological therapy and referral for psychological interventions. In April 2017, recommendation 1.1.1.2 was updated in line with more recent guidance on recognition and referral for suspected cancer. This recommendation is dated [2017]. Recommendation 1.1.1.3 was removed as it was no longer needed after the changes to recommendation 1.1.1.2.