163 cases of supratentorial astrocytomas and glioblastomas were evaluated retrospectively after close-meshed observation and treatment. We attached the greatest importance to the reevaluation of already known prognostic parameters and to the temporal analysis of the course of gliomas. We could confirm the influence of the histologic grade on the survival time. Histologic grading by means of immunohistochemistry proved to be more precise than grading only by means of HE staining. Furthermore, the patient's age was one of the most important prognostic variables for survival time after operation. Other factors were the first preoperative Karnofsky rating, the preoperative diameter of the tumour, the duration of preoperative symptoms and the interval between operation and diagnosis of tumour recurrence as well as between tumour recurrence and reoperation. Epileptic seizures as preoperative symptoms were found to be far less prognostic for survival time. Localisation of the tumour, other preoperative symptoms, Karnofsky rating before reoperation and the extent of tumour resection proved to be of no importance for survival time.