Background Transurethral resection of the prostate (TURP) is the standard operation for benign prostatic obstruction (BPO). Thulium laser transurethral vaporesection of the prostate (ThuVARP) vaporises and resects the prostate using a technique similar to TURP. The small amount of existing literature suggests that there may be potential advantages of ThuVARP over TURP. Objective To determine whether or not the outcomes from ThuVARP are equivalent to the outcomes from TURP in men with BPO treated in the NHS. Design A multicentre, pragmatic, randomised controlled parallel-group trial, with an embedded qualitative study and economic evaluation. Setting Seven UK centres – four university teaching hospitals and three district general hospitals. Participants Men aged ≥ 18 years who were suitable to undergo TURP, presenting with bothersome lower urinary tract symptoms (LUTS) or urinary retention secondary to BPO. Interventions Patients were randomised 1 : 1 to receive TURP or ThuVARP and remained blinded. Main outcome measures Two co-primary outcomes – patient-reported International Prostate Symptom Score (IPSS) and clinical measure of maximum urine flow rate (Qmax) at 12 months post surgery. Results In total, 410 men were randomised, 205 to each arm. The two procedures were equivalent in terms of IPSS [adjusted mean difference 0.28 points higher for ThuVARP (favouring TURP), 95% confidence interval (CI) –0.92 to 1.49 points]. The two procedures were not equivalent in terms of Qmax (adjusted mean difference 3.12 ml/second in favour of TURP, 95% CI 0.45 to 5.79 ml/second), with TURP deemed superior. Surgical outcomes, such as complications and blood transfusion rates, and hospital stay were similar for both procedures. Patient-reported urinary and sexual symptoms were also similar between the arms. Qualitative interviews indicated similar patient experiences with both procedures. However, 25% of participants in the ThuVARP arm did not undergo their randomised allocation, compared with 2% of participants in the TURP arm. Prostate cancer was also detected less frequently from routine histology after ThuVARP (65% lower odds of detection) in an exploratory analysis. The adjusted mean differences between the arms were similar for secondary care NHS costs (£9 higher for ThuVARP, 95% CI –£359 to £376) and quality-adjusted life-years (0.01 favouring TURP, 95% CI –0.04 to 0.01). Limitations Complications were recorded in prespecified categories; those not prespecified were excluded owing to variable reporting. Preoperative Qmax and IPSS data could not be collected for participants with indwelling catheters, making adjustment for baseline status difficult. Conclusions TURP was superior to ThuVARP in terms of Qmax, although both operations resulted in a Qmax considered clinically successful. ThuVARP also potentially resulted in lower detection rates of prostate cancer as a result of the smaller volume of tissue available for histology. Length of hospital stay after ThuVARP, anticipated to be a key benefit, was equal to that after TURP in this trial. Overall, both ThuVARP and TURP were effective procedures for BPO, with minor benefits in favour of TURP. Therefore, the results suggest that it may be appropriate that new treatment alternatives continue to be compared with TURP. Future work Longer-term follow-up to assess reoperation rates over time, and research into the comparative effectiveness of ThuVARP and TURP in large prostates. Trial registration Current Controlled Trials ISRCTN00788389. Funding This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 41. See the NIHR Journals Library website for further project information.