Stellate ganglion block is a selective sympathetic blockade affecting the head and neck, and the upper extemity. It is an important method which has been used most frequently in neuro-pain clinic due to its wide range of indications. The authors attermpted to define the minimal volume of local anesthetic which need for successful stellate ganglion block by using 1% mepivacaine HCl mixed with dye. In 40 heathy volunteers, two different volumes, 3 ml in the group 1 (n=20) and 4 ml in the group 2 (n=20), were injected by an anterior paratracheal technique at the sixth cervical vertebral level. We compared the degree in sympathetic blockade by clinical sings and symptoms and also checked the spread range of dye by plain X-ray. With seven criteria for an effective block. mean score was 5.7 in group 2, while 3.4 in group 1. These results suggest that 4 ml of local anesthetic are adequate for a successful stellate ganglion block.