We report 25 verified cases of well-differentiated cerebral astrocytomas in adults treated between 1978 and 1988. All patients were diagnosed by computed tomographic (CT) scans, with 5 undergoing a craniotomy for debulking and 20 undergoing a biopsy alone. The median survival for the entire group was 8.2 years, the longest survival yet reported for a series of patients with these tumors. A review of the literature suggests that the longer survival observed in more recent series is the result of the earlier diagnosis of tumors afforded by modern brain imaging. Twenty of our patients presented with seizures in the absence of any other focal findings and would probably not have had a biopsy in the era before CT scans until their tumors had progressed. Only 8% of our patients had papilledema at the time of presentation, in contrast to almost half of the patients with low-grade astrocytomas reported before 1975, supporting the hypothesis that patients in the CT era are diagnosed earlier. None of our patients died from progressive low-grade disease. One patient died from a squamous cell cancer, and 7 died as a consequence of their tumors dedifferentiating into a more malignant astrocytoma or glioblastoma multiforme, with a median time of approximately 5 years after the diagnosis. Our findings, together with the available data in the literature, suggest that death from a focal low-grade astrocytoma, in the absence of malignant degeneration, may be a rare event. Consequently, future therapeutic efforts should be targeted at preventing dedifferentiation.(ABSTRACT TRUNCATED AT 250 WORDS)