Experimental results of nitrogen molecular laser irradiation on tumors found in several groups of white rats,the observation of changes in their main internal organs and immunized organs,and the pathological changes in their tumors are described.Investigations in cancer cell culture after the application of nitrogen molecular laser irradiation on sarcomas S180 of white mice is also reported.These indicate that the irradiation not only strengthen the immunity of the body,but also arrest the growth of tumors. These show that the irradiation may be a comparatively ideal unspecific origin of stimulation to step up the organic immunization and nitrogen molecular laser may be used as a new auxiliary means to cure malignant tumors.