Aim: To clarify whether there are anatomical changes in tunica albuginea and corpora cavemosa in aged rats. Methods: Seventeen male Sprague-Dawley rats were divided into three groups based on age. Group A consisted of young rats (9 weeks), Group B, middle aged rats (14 weeks) and Group C, old rats (62 weeks). The penile samples were obtained and observed under a scanning electron microscope. Results: The thickness (mean ± SD) of the tunica albuginea was 0.14 ± 0.02, 0.16 ± 0.03 and 0.06 ± 0.02 mm in Groups A, B and C, respectively. The tunica albuginea of group C was significantly thinner than those of the other two groups ( P ＜ 0.05) and the elastic fibers were diminished in the old rats. In the corpora cavemosa of old rats, the intracavemous pillars were irregular, in which many large collagen fibers could be observed, and the smooth muscle and elastic fibers were reduced. Conclusion: In old rats, the tunica albuginea became thinner with diminished elastic fibers; the collagen fibers of corpora cavemosa were increased while the smooth muscle and elastic fibers were reduced.