Thirty-six cases of astrocytoma (10 cases each of gradeⅠ and grade Ⅱ,and eight cases each of grade Ⅲ and grade Ⅳ) with definite followup data were studied with microspec-trophotometry on Feulgen stained slides to determine the nuclear area and the DNA content.10 specimens of normal brain tissue or brain tissue with gliosis were observed with the same technique.It was found that there was no significant difference of the nuclear size between the cells of grade Ⅰ astrocytoma and those with gliosis,but the DNA content was significantly higher in the former than in the latter.And there was also defference of the histograms between the 2.The higher the grading of astrocytoma,the larger the nuclear area,and the higher the DNA content.The peak values of the histograms were shifted rightward with a scattering of the values.In addition,along with the increase of DNA index,there was a decline of the survival curve of the patients with an obvious shortening of the survival time.The findings suggest that nuclear DNA quantitation can serve as an auxiliary tool to differentiate grade.I astrocytoma from gliosis,to grade astrocytomas and to predict the prognosis.