We present the results of the examination of prognostic markers in 40 children suffering from brain tumors. Prognostic markers such as amplification of the N-myc and c-myc, deletion of the 17p, and DNA ploidy are indispensable factors for the determination of diagnosis. An increased number of c-myc gene copies was found in malignant brain tumors, especially embryonal, more often than reported in the literature. N-myc amplification occurs in our group seldom, but it seems to be a sign of worse prognosis in glial and embryonal brain tumors. DNA aneuploidy was not found very frequently, but in high-grade tumors only.