Transurethral Needle Ablation of the prostate (TUNA) is a new thermal ablation treatment for benign prostatic hyperplasia (BPH) utilizing radiofrequency electric current delivered by needles into the depth of the prostate to produce an area of coagulative necrosis. A pilot study of 10 patients in urinary retention was undertaken to assess the procedure. After treatment, nine patients voided at a median time of 3 days, although a further two required transurethral resection because of chronic infection in one and chronic urinary retention in the other. At 3 months' follow-up, the mean Qmax was 13.0 mL/sec, the mean AUA Symptom Score was 9.1, and the mean quality of life score was 1.6. The mean Pdet fell from 73.3 to 39.0 cm H2O. On transrectal ultrasound at 3 months, cystic lesions were seen in two patients, with a third having large cavities. A 10.2% reduction in mean prostatic volume, from 48.8 cc to 43.8 cc, was noted but considered to be not significant. On endoscopy at 3 months, mucosal retraction was seen in seven patients, with cavities in two patients. Histologic study in patients undergoing transurethral resection 4 to 6 months after TUNA showed necrosis and fibrosis. It is considered that an area of coagulative necrosis is produced by TUNA that resolves either by scar formation with retraction or by liquefaction with cyst formation. If the lesion communicates with the urethra, a cavity may form, which is undesirable. Our early experience is encouraging. The TUNA treatment is effective, can be given without anesthesia, and should be either a day case or an office procedure. It should prove to have a significant place in the treatment of BPH.