Recent years have witnessed important developments in natural family planning (NFP), which is based on the observation of fertile and infertile periods of the menstrual cycle, so that the couple is able to know when sexual intercourse may lead to a pregnancy. A review of the main studies regarding the effectiveness of NFP showed a decrease in the Pearl Index and life table values from the early 1980s to date, indicating that progress both in the teaching and in the application of these contraception, methods has been achieved. The main cause of lack of success seems to be the misapplication of NFP rules, whereas the errors due to the method itself are few. Furthermore, it seems that the symptothermal method might give better results than the ovulation method, even though no comparative study has been carried out, and that the first studies on the lactational amenorrhea method show encouraging results. Finally, it seems that NFP is best suited for 'spacers' of pregnancies, rather than for 'limiters'. Indeed, the former are more likely to show good compliance, since the sexual abstinence periods are limited and an unwanted pregnancy is not regarded as a completely negative event.