Palmar hyperhidrosis (PH) is common in Orientals from subtropical areas. Many therapeutic modalities are used in practice, but none has proved to be entirely satisfactory. We have developed a new therapeutic technique by combining a video thoracoscopic system with a surgical laser unit (both waveguide CO2 laser and fibre-optic Nd:YAG laser). The operation was performed under general anaesthesia with alternative one-lung ventilation. With this technique, we are able to identify the sympathetic trunk on the TV screen and confirm its proper level with accurate ablation by intraoperative vasomotor monitoring. Consequently, an adequate sympathectomy can be definitely achieved through laser extirpation. We have successfully treated 300 PH patients with this technique from 1990 to 1992. The ages ranged from six to 63 years with a mean of 26.6. There were 125 males and 175 females. Most patients underwent en bloc ablation of the T2 segment which includes a major part of the T2 ganglion with its adjacent trunk which overlays the T2 rib head. All of them obtained a satisfactory relief of PH except 13 patients. The procedure did not result in a change of vital signs. There was neither obvious injury to lung nor bleeding. No Horner's syndrome was produced. The commonest complication was compensatory hyperhidrosis in various degrees encountered in about half of the cases. Two-thirds of the patients were followed up for more than 12 months and only three had recurrence. Based on our experience, the technique is considered to be a minor and safe procedure and able to achieve a definite and long-lasting therapeutic effect. It causes minimal discomfort and scarring. Particularly, the operation time and hospital stay were markedly shortened in comparison with other conventional open sympathectomy procedures.