We propose an original methodology which improves the accuracy of the prognostic values associated with conventional morphologically‐based classifications in supratentorial astrocytic tumors in the adult. This methodology may well help neuropathologists, who must determine the aggressiveness of astrocytic tumors on the basis of morphological criteria. The proposed methodology comprises two distinct steps, i.e. i) the production of descriptive quantitative variables (related to DNA ploidy level and morphonuclear aspects) by means of computer‐assisted microscopy and ii) data analysis based on an artificial intelligence‐related method, i.e. the decision tree approach. Three prognostic problems were considered on a series of 250 astrocytic tumors including 39 astrocytomas (AST), 47 anaplastic astrocytomas (ANA) and 164 glioblastomas (GBM) identified in accordance with the WHO classification. These three problems concern i) variations in the aggressiveness level of the high‐grade tumors (ANA and GBM), ii) the detection of the aggressive as opposed to the less aggressive low‐grade astrocytomas (AST), and iii) the detection of the aggressive as opposed to the less aggressive anaplastic astrocytomas (ANA). Our results show that the proposed computer‐aided methodology improves conventional prognosis based on conventional morphologically‐based classifications. In particular, this methodology enables some reference points to be established on the biological continuum according to the sequence AST→ANA→GBM.