We studied 23 pediatric high-grade astrocytomas by comparative genomic hybridization. Chromosomal imbalances were found in 10 of 10 anaplastic astrocytomas and 11 of 13 glioblastomas and consisted of +1q (43%), +3q (26%), +1p, +2q, +5q (22%), -22q (34%), -6q, -10q (30%), -9q, -11q, -13q, -16q, and -17p (22%). Anaplastic astrocytomas frequently showed +5q (40%), +1q (30%), -22q (50%), -6q, -9q (40%), and -12q (30%); glioblastomas +1q (54%), +3q (38%), +2q, +17q (23%), -6q, -8q, -10q, -13q, and -17p (31%). Minimal common regions mapped to +1q21-41, +3q27-qter, +2q31-32, +5q14-22, -22q12-qter, -10q23-25, -6q25-qter, -9q34.2, -11q14-22, -16q22-qter, and -17p. High-level gains were located on 1q (7 cases), 2q, 7q (4 cases), 3q (3 cases), 9, 17q (2 cases), 4q, 8q, 18, and 20q (1 case). A significantly shorter survival was found for anaplastic astrocytomas showing +1q (P: < 0.05), MIB-1 proliferation index >25% (P: < 0.001) and glioblastomas (P: < 0.05). Compared with adult cases, +1p, +2q, and +21q as well as -6q, -11q, and -16q were more frequent in pediatric malignant astrocytomas. Among the latter +5q, -6q, -9q, -12q, and -22q were characteristic for pediatric anaplastic astrocytomas and +1q, +3q, +16p, -8q, and -17p for pediatric glioblastomas. Our results show that chromosomal aberrations differ between pediatric anaplastic astrocytomas and glioblastomas as well as between pediatric and adult high-grade astrocytomas, supporting the notion of a different genetic pathway. Furthermore, gains of chromosomal material on 1q might be correlated with a worse prognosis in pediatric anaplastic astrocytomas.