Fifty-eight fetal and neonatal temporal bones were studied to evaluate the mechanisms of development of the hiatus of the facial canal, hypotympanic fissures, periotic duct, tympanomeningeal fissures, and fetal inner ear vascularity. These were correlated with the clinical pathologic entities of temporal bone trauma, glomus jugulare tumor extension within the temporal bone, CNS-temporal septic conduits, and inner ear vascularity. Temporal bone developmental anatomy and histopathology provide rich sources of information on which to base the scientific and clinical study of otology.