This study was realized to illustrate and analyze the ultrastructural mitochondrial pathology in human astrocytic tumors. Tumoral biopsies of 10 patients with pathological diagnosis of astrocytic tumors by means of transmission electron microscopy were examined. Mitochondria exhibits heterogeneous morphology in all the cases. Mitochondrial swelling with partial or total cristolysis was the most constant alteration observed. Mitochondrial fusion-fission phenomena have been demonstrated. These findings suggest that the majority of astrocytoma cells are incompetent to produce adequate amount of energy by means of oxidative phosphorylation. Ultrastructural mitochondrial pathology indicates that possibly both glycolytic inhibition and inhibition or down-regulation of mitochondrial respiration would be a potential tool for future therapeutic strategies in cases of human astrocytic tumors.