Our previous karyotypic studies of malignant human gliomas have demonstrated that their most consistent early or primary gross changes include gains of #7, losses of #10, #22, and the gonosomes, and the presence of double minutes. Karyotypes of 15 additional malignant human gliomas reported here have confirmed these observations and, by enlarging our series, we can now show that in addition to double minutes, certain other gross structural abnormalities also are clearly associated with the early evolution of this type of tumor. The most prevalent deviations are deletions and translocations involving 9p. Other chromosomes commonly involved in rearrangements are #1, #6, and #13, and less frequently #7, #11, and #16.