Limited studies have described the ultrastructure of trachea of late fetal and neonatal hamsters but the effects of parturition and the onset of breathing on structure have not been discussed. This study describes morphological features of ante- and post-partum tracheal mucosa and submucosa and contrasts these features in fetal and neonatal hamster siblings. Significant differences between these siblings are noted in tracheal cells interfacing the lumen. Such cells of the fetal animals usually possessed cytoplasm of medium electron density with cisternal rough endoplasmic reticulum (RER). Surface membranes of these cells possessed numerous microvilli. In contrast, corresponding cells of post-natal animals often had lucent cytoplasm with mostly tubular or vesicular RER. Surface membranes of these cells possessed microplicae (microridges). This study also considers characteristics of fetal and neonatal tracheal development including: lomasome-like structures in secretory cells; dichotomous forms of oligocilia in mucosal and submucosal cells; intramembranous particles of hemidesmosomes; particles and mitochondria associated with desmosomes; and affiliations of ciliary basal bodies with the cytoskeleton, cell membrane, and with endoplasmic reticulum.