Mutations of the p53 gene are one of the most frequent genomic alterations of human tumours of astrocytic lineage. Because the physiological role of this gene is a suppression of cellular proliferation and growth, the overexpression of p53-protein may correlate with the expression of PCNA or Ki-67, established markers of cell proliferation. Paraffin-embedded surgical specimens from 60 human astrocytomas (9 pilocytic tumours, 12 WHO grade II, 9 anaplastic astrocytomas [WHO grade III] and 30 glioblastomas [WHO grade IV]) were stained with anti-PCNA (PC10), anti-p53(DO-7) and anti-Ki-67 antibodies (DAKO). Approximately 40% of all the cases were p53-protein immunopositive (53.3% glioblastomas, 33.3% anaplastic, 41.7% low grade astrocytomas but no pilocytic tumor). Statistical analysis did not reveal statistically significant correlation between p53-immunopositivity and PCNA or Ki-67 labeling indices. The Ki-67- and PCNA LI-s were statistically correlated, and the former better discriminated groups of different grades of malignancy.