Effect of He Ne laser irradiation of the cervicales anteriores region and of acupoint irradiation on rabbits is studied. The nodi lymphatici cervicales anteriores were observed by optical microscopy and transmission electron microscopy. The serum IgG was measured with a simple immunodiffusion method. The results showed that the ultrastructures of many kinds of cells in the lymph nodes both region irradiated and acupoint irradiated were changed. The function of the cells appeared activized. The serum IgG of the acupoint irradiation groups was much more than the control group. It was suggested that He Ne laser enhancing of cellular and humoral immunities of the organism was on the basis of changes of the cell ultrastructures. In conclusion, the immunity of the entire organism was enhanced by the laser acupoint irradiation, but the region irradiation only improved the immuniactivities of the irradiated region.