In the present study we have checked whether photodynamic therapy (PDT) may influence concentration of basic Fibroblast Growth Factor (bFGF) in in vivo conditions. We have implanted malignant tumor, i.e. BFS1 fibrosarcoma into BALB/c mice and have them treated using well established photosensitizer, hematoporphyrin derivative and new compound, hydroxygallium (III) phthalocyanine tetrasulfonic acid tetrasodium salt, BON-6. The administration of those compounds was followed by light irradiation using a halogen lamp at proper wavelengths. Our results indicate that in vivo photodynamic therapy may cause a significant decrease in bFGF concentration and this phenomenon is accompanied by prolongation of survival of treated animals.