This experimental clinical stuay was started in 1985. Experiment involved 1010 mice and rats with 10 different types of inoculated a nd induced tumors as well as 10 dogs and cats with 7 malignant and 9 benign spontaneous tumors. The experimental pant of this study was aimed at comparing the action upon the tumors of Hematoporphyrin derivative ( HpD ) , when agents is excita ted in loco by light or gammaradiation . In 24 72 hours ,followina the injection of HpD into tumors bearing animals ,. the tumors were irradiated by the red light or by the gammaradiatiom of radio - active cobalt ( 60 Co ) using the dose 2 3 Gy. Such treat ment was applied only once. The positive effect of both procedures was observed in the majority of cases witn inoculated tumors and in all cases of induced and spontaneous malignant tumors. PDT has suc cessfully found its way in the Head and Neck surgery department of Lithuanian 0 ncology Centre since 1989. At first ,it was used as the palliative treatment, and later on as the radical method of treat ment. The total o 42 patients has been treated : 6 previously un treated patients, the others had the recurrent desease, or tumors non responsive to other modalities . There were 72 cancer foci in 42 pa tients treated by 108 courses of PDT in all. Three new and effective PDT methods were proposed y us I Q' Applying PDT for patients with oral cancer we injected photosensibilizator into the artery branch supplying the tumor. Canu la was installed into the superficial temporal artery and Hernatoporphyrin ( 5 mg ) was injected with immediate irradiation of tumor with laser light ( each cm2 of the tumor absorbed the energy dose of 200 J.) Within the next 24 - 4-8 hours full tumor tissue necrosis was found. If the effect of such PDT course was not adecuate , this treatment has to be repeated. 2 ) The second treatment modality was applied for the patients with cytologically verified melanoma. Following the ultrasonic exarnina tion of melanoma depth, PDT was applied preoperatively ( the energy dose to be absorbed by each cm2 of melanoma was thcr.eased up to 250 J.) with wide mela noma excision 5 to 7 days later. Histological study showed no melanoma tissue. 3 .) Hematoporphyrth ( Hp ) excitation by amrnaradiation was used. Intravenous Hp was administered and 48 hours later, the tumors were 1radiated with the gammaradlatlon of radioactive coba1t, using the single dose of 3 Gy . This treatment was named by us Gamnadynarnic therapy ( ODT ) . GDT was used both : alone and in cornbthatlon with PDT. The total of 2 patients has been treated. The best effect of GDT was observed in patients with osteoenic sarcoma ( 2 patients ) and melanoma ( 8 patients ). Keywords ; PDT , gamma irradiation, G-ammadynamic therapy, melanoma, oral cancer.