30 patients with primary or recurrent malignant brain tumors (9 primary, 18 recurrent malignant gliomas, 1 malignant meningioma, 2 melanomas) were treated altogether 37 times by photodynamic therapy (PDT) whether after intravenous, intraarterial or direct intratumoral sensitisation by hematoporphyrin (HPD) after conventional surgical removal of the tumor mass. The light was produced by an Argon pumped dye laser at doses varying from 40-220 J/cm2. A single dose of radiation of 4 Gy was administered to 18 patients immediately after PDT. The 9 patients with primary glioblastomas received in addition a full course of radiation therapy. The histological specimens taken during PDT demonstrated tumor necrosis, with oedema of normal brain tissue adjacent to the tumorbed. The median survival of patients with multiple recurrences and various radio- and chemotherapeutic modalities was 6 months (range 4-13 months). 9 patients with primary manifestation of a glioblastoma had a median survival of 19 months (0.5-29 months). Increased phototoxicity of the skin was the only side effect of PDT and did not reduce the quality of life of the patients.