ABSTRACT - The purpose of this review article is to present a 50-year perspective of research on mechanical method for limiting male dog reproduction by the use of therapeutic ultrasound. Ultrasound's potential as a male contraceptive was first reported by Fahim et al. in 1977 where it was shown that a single application could result in a reversible dramatic loss of germ cells. If the method can be made permanent, a noninvasive method for controlling domestic pet populations could be developed, although standard treatment is not yet identified. More recent studies in 2000s by our research group demonstrated that tree treatment