BACKGROUND: It was frequently noticed in the course of performing a two-needle sympathectomy, that satisfactory spread of contrast solution could be produced by injection through only one of the needles. This led to a closer examination of the merits of single-needle technique. METHODS: Forty patients were randomized into two groups. Patients in the single-needle group (n = 20) were injected at the second or third lumbar sympathetic ganglia, while patients in the two-needle group (n = 20) were injected at the second and third lumbar sympathetic ganglia. Lumbar sympathetic blocks were performed using 3 ml of alcohol and the spread of injectate was verified with C-arm fluoroscopy. The indicators of a successful sympathetic block are increasing skin temperature, decreasing pain, and anhidrosis in the distal extremity. RESULTS: The duration of anhidrosis was 12.2 2.6 months (mean SD) in the single-needle group versus 13.6 3.6 months (mean SD) in the two-needle group. CONCLUSIONS: As these results were not significantly different from those obtained in patients having a two-needle sympathectomy, blockade of the single-needle technique under C-arm fluoroscopy is considered to be effective for a neurolytic lumbar sympathectomy.