The surest form of male contraception is vasectomy; its only problem is reversibility, since reanastomosis is effective in only 20% of cases. The other, and most common, forms of male contraception are the use of a condom and coitus interruptus; both ways are only relatively secure. Injections of testosterone can block spermatogenesis, while injections of Depo-Provera can block sperm maturation and motility; the same effects can be achieved by treating the testicles with ultrasounds or with certain types of radiation. The occlusion of both vasa deferentia, either with valves or by surgery, is still at an experimental stage.