We report the use of photodynamic therapy (PDT) in the treatment of 20 patients with newly diagnosed malignant supratentorial gliomas. There were 10 males and 10 females; their mean age was 56 years and the mean Karnofsky score was 75. Eleven patients had glioblastoma multiforme (GBM) and 9 had malignant astrocytoma (MA). Intravenous porphyrin photosensitizer was administered 12-36 h prior to surgery and photoillumination. At operation all patients had the tumor subtotally resected followed by intraoperative cavitary photoillumination. Interstitial photoillumination using fibers with 2-cm diffusing tips supplemented the cavitary illumination in 3 patients. The total light energy delivered ranged from 570 to 4050 J (median = 1260 J). The energy density ranged from 15 to 110 J/cm2 (median = 32 J/cm2). All but two had postoperative radiation therapy (5000 cGy in 5 weeks). No untoward effects of radiation in conjunction with PDT were identified. There was 1 postoperative death and 1 patient had a persistent increase in postoperative neurological deficit. The median survival of these 20 patients with newly diagnosed malignant gliomas was 44 weeks with a 1- and 2-year survival of 40 and 15%, respectively. The median survival of these patients with newly diagnosed GBM was 37 weeks with a 1- and 2-year survival of 35 and 0%, respectively, and the median survival for MA was 48 weeks with a 1- and 2-year survival of 44 and 33%, respectively. Six patients with a Karnofsky score of > 70 who received a light dose of > 1260 J (mean energy density = 62 +/- 20 SEM J/cm2) had a median survival of 92 weeks with a 1- and 2-year survival of 83 and 33% respectively. Patients with malignant astrocytic tumors (GBM and MA) have a very poor prognosis. Nevertheless PDT is safe in newly diagnosed patients with supratentorial malignant gliomas who undergo postoperative radiation and appears to prolong survival in selected patients when an adequate light dose is used. Further improvement in survival may be expected with higher light doses.