BACKGROUND: There have been unexpected cases of failed alcoholic sympathectomy, even though satisfactory effects had been obtained in test blocks with a mixture of contrast media and local anesthetics. It was plausible to suspect the contrast media as a cause of the failure of alcoholic sympathectomy. So, the purpose of this study was to evaluate whether the contrast media can hinder the action of alcohol in alcoholic sympathectomy or not. METHODS: In Sprague - Dawley rats (200 300g), thoracic paravertebral sympathetic chains were exposed and planned regimens were injected in these regions. The rats were divided randomly into seven groups, group C (control group), group D (administration of dye just after exposure), group D-A30 (administration of dye just after exposure, administration of alcohol 30 min. after dye), group A30 (administration of alcohol 30 min. after exposure), group D-A0 (administration of dye just after exposure, administration of alcohol just after dye), group D-A60 (administration of dye just after exposure, administration of alcohol 60 min. after dye) and group D-A90 (administration of dye just after exposure, administration of alcohol 90 min. after dye). Degrees of cytoplasmic contraction were evaluated in the ganglion cells of each member of the experimental groups. RESULTS: The contraction ratios of cytoplasms in group D-A30 and A30 were greater than that of group C and D. The contraction ratios of cytoplasm in group D-A60 and D-A90 were greater than those of group D-A0 and D-A30. CONCLUSIONS: According to our results, the contrast media seems to hinder the action of alcohol in alcoholic sympathectomy.