The hippocampus is one of the areas most vulnerable to histopathological changes, and such changes may yield useful information in forensic medicine. We found that glial fibrillary acidic protein (GFAP)-positive astrocytes are frequently found in the hippocampus of consecutive series of forensic brains, distributed predominantly in the hippocampal CA4 and hippocampal sulcus (HS) regions. The present study counted GFAP-positive astrocytes in these regions and investigated associations with age, cause of death and postmortem time. Significant correlations were found between age and number of GFAP-positive astrocytes in both CA4 and HS regions. Number of GFAP-positive astrocytes increases in an age-dependent manner, but no correlations were noted between number of GFAP-positive astrocytes and postmortem time and cause of death. Number of GFAP-positive astrocytes in the hippocampus may provide useful information for age estimation.