Objective To compare the efficacy and frequency of complications of transurethral interstitial laser coagulation (ILC) and transurethral microwave thermotherapy (TUMT) with transurethral resection or incision of the prostate (TURP/TUIP) in patients with symptomatic benign prostatic hyperplasia (BPH). Patients and methods Forty-eight patients were randomized to undergo ILC, 46 to TUMT and 24 to TURP/ TUIP; they were followed for 6 months and the outcome analysed on an intention-to-treat basis. Results At 6 months the symptom scores and maximum urinary flow rate (Q max ) had improved significantly in all groups. At 6 months the mean symptom score was 9.2 in both experimental groups and 6.8 in the control group ( P > 0.05); the mean Q max was 20.6 mL/s in the control group, 16.2 in the ILC group ( P > 0.05 vs control) and 13.2 in the TUMT group ( P < 0.05 vs. the control group). In the TUMT group patients developing urinary retention afterward had a significantly greater increase in Q max than those who did not. The types of complications in the three groups varied. Urinary tract infection occurred frequently in the experimental groups, especially after ILC, whereas the 'well-known' complications of TURP occurred in the control group.Overall, 36% in the ILC, 54% in the TUMT and 73% in the control group had no complications (retrograde ejaculation excluded) during the first 6 months. One patient in the TUMT group underwent TURP after 3 months, whereas no patients in the ILC or the control group were re-treated for BPH within the first 6 months. Conclusion In the short term both ILC and TUMT are reasonable alternatives to standard transurethral surgery for symptomatic BPH, where the reduction of symptoms is the primary goal of treatment. However, both ILC and TUMT were associated with morbidity, although the complication profiles differed from those after TURP/TUIP. Both ILC and TUMT seem advantageous in some patients because of the reduced risk of bleeding and the eliminated risk of TUR syndrome, and because TUMT only requires local anaesthesia. Thus, as neither treatment is better in all aspects, the advantages of one technique over the other must be weighed when deciding how to treat each patient.