Sterilization is a surgical technique leaving a male or female unable to procreate. It is one of the methods of birth control.

Sterilization is also a term used for the process of removing or killing all microorganisms from an object, commonly done for medical instruments.

The rest of this article refers to sterilization as a surgical means of removing fertility in humans.

  • A vasectomy in males. The Vas Deferens, the tubes which connect the testicles to the prostate, are cut and closed. This prevents sperm produced in the testicles to be in the semen fluid (mostly produced in the prostate) that is ejaculated.
  • A tubal ligation in females. The Fallopian tube, which allows the sperm to fertilize the ovum and would carry the fertilized ovum to the uterus, is closed.
The closing of either type of tube can be done in several different ways, some of which are more permanent or guaranteed to work than others. The tube can be
  • clamped off
  • cut off
  • tied off
  • blocked

Vasectomy should not be confused with castration: vasectomy does not involve removal of the testicles and it affects neither the production of male sex hormones (mainly testosterone) nor their secretion into the bloodstream. Therefore sexual desire (libido) and the ability to have an erection and an orgasm with an ejaculation are not affected. Similarly, in females' hormone production, libido and the menstrual cycle are not affected.

When the vasectomy is complete, sperm can no longer exit the body through the penis and it seems that they penetrate the blood-testes barrier. Normally, the barrier keeps the immune system separate from the reproductive system. When the barrier is compromised usually by vasectomy, injury, or even a simple puncture from a biopsy, the two systems interface. This usually results in the development of anti-sperm antibodies.

In order to allow for reproduction (via artificial insemination) after vasectomy, some men opt for cryostorage of sperm before sterilization.

In animals, castration (called neutering) and salpingo-oophorectomy (removal of the ovaries and Fallopian tubes, or spaying) are used to prevent conception and, in females, heat, and to prolong the animal's life. Owners of pets such as cats and dogs are urged to have their pets spayed or neutered in order to prevent increase in the population of stray animals.