This chapter offers a discussion of basic normal ejaculatory duct embryology, anatomy, and physiology to lay a foundation for an understanding of the clinical findings and treatment of obstruction. In the male the mesonephric duct continues to develop into the epididymis, vas deferens, seminal vesicle, and ejaculatory duct. The remnant Müllerian structures in the male are the prostatic utricle and appendix testis, and in some men remnant Müllerian duct structures can be found in the midline of the prostate as Müllerian duct cysts. The ultrasonographic diagnosis of ejaculatory duct obstruction is based upon the finding of dilation of the seminal vesicles and abnormalities in the region of the ejaculatory ducts. Stricturing of the resected ejaculatory ducts may represent the most significant complication in regard to fertility, and may occur immediately or in a delayed fashion.