Condoms are rubber or latex sheaths which prevent entry of sperm into cervix of female genital tract and subsequent fertilisation. They may fail when the sheath ruptures or is damaged. Coitus interruptus involves removal of penis from vagina just before ejaculation during copulation. But as some semen may be released before proper ejaculation or sometimes ejaculation may be sudden not allowing withdrawal thus they have a sufficient chance of failure. Periodic abstinence involves abstaining from copulation during ovulatory phase of menstrual cycle but there may be mistakes in calculation and interpretation of cycle. Vasectomy involves surgical removal of a part of vas deferens, thus the sperm from testis cannot be mixed with semen. This method has more than 99% rate of success.