BACKGROUND: A recent randomised controlled trial (RCT) of acupuncture as a treatment for irritable bowel syndrome (IBS) demonstrated sustained benefits over a period of 12 months post-randomisation. AIM: To extend the trial follow-up to evaluate the effects of acupuncture at 24 months post-randomisation. METHODS: Patients in primary care with ongoing IBS were recruited to a two-arm pragmatic RCT of acupuncture for IBS. Participants were randomised to the offer of up to 10 weekly sessions of acupuncture plus usual care (n=116 patients) or to continue with usual care alone (n=117). The primary outcome was the self-reported IBS symptom severity score (IBS SSS) measured at 24 months post-randomisation. Analysis was by intention-to-treat using an unstructured multivariate linear model incorporating all repeated measures. RESULTS: The overall response rate was 61%. The adjusted difference in mean IBS SSS at 24 months was -18.28 (95% CI -40.95 to 4.40) in favour of the acupuncture arm. Differences at earlier time points estimated from the multivariate model were: -27.27 (-47.69 to -6.86) at 3 months; -23.69 (-45.17 to -2.21) at 6 months; -24.09 (-45.59 to -2.59) at 9 months; and -23.06 (-44.52 to -1.59) at 12 months. CONCLUSIONS: There were no statistically significant differences between the acupuncture and usual care groups in IBS SSS at 24 months post-randomisation, and the point estimate for the mean difference was approximately 80% of the size of the statistically significant results seen at 6, 9 and 12 months. TRIAL REGISTRATION NUMBER: ISRCTN08827905.