An international team evaluated the agreement on diagnoses and prescription of irritable bowel syndrome among traditional Chinese medicine (TCM) practitioners. Consecutive irritable bowel syndrome patients were interviewed independently by four TCM practitioners. The study was divided into three phases: (i) blinded individual assessment, (ii) discussion to achieve consensus on diagnosis and treatment, (iii) individual assessment based on consensual diagnostic criteria. Patients with other causes of diarrhoea were recruited as controls in phase (iii). Percentage agreement and kappa-value in diagnosis, treatment principle and regime were determined. Thirty-nine irritable bowel syndrome patients were assessed in phase (i) whereas 65 irritable bowel syndrome patients and 17 non-irritable bowel syndrome controls were studied in phase (iii). The mean agreement rates in diagnosis, treatment principle and regimen were: 57, 58 and 52% for phase (i) and 80, 81 and 80% for phase (iii). Accordingly, there was significant improvement in the mean kappa-values in diagnosis (0.11–0.34) and treatment principle (0.16–0.37) but not in the treatment regime.