The ideal contraceptive method should be totally effective and totally reversible totally safe and totally acceptable. Such a method has not yet been found. Effectiveness is difficult to measure since it can be theoretical but also practical taking into account strength of motivations and human errors. No contraceptive agent is 100% effective but some have a failure rate that is less than 2/100 woman years. Safety can be immediate as with spermicidal contraceptives or projected into the future as with the use of oral contraceptives about whose side effects not much is really known. Safety must also be considered in regard to future fertility and to a future eventual fetus. Acceptability is variable depending on the individual couple. It is based on cost facility of application moral and religious opinion absence of pain absence of unaesthetic gestures or positions and last but not least a countrys legal code.