A large proportion of couples rely on behavioral methods of contraception, at least intermittently or at some point in their lives. These methods rely on knowledge about male and female reproductive physiology and the menstrual cycle rather than medications, herbs, devices, or barriers to prevent pregnancy. Behavioral methods can be divided into two categories: methods that do not rely on the menstrual cycle (i.e., abstinence or coitus interruptus) and methods that rely on the menstrual cycle. Methods that rely on the menstrual cycle can be further subdivided into Fertility Awareness Methods (FAM) and “Natural” Family Planning (NFP). FAM includes methods that rely on women to monitor physiologic changes during their menstrual cycle, whereas NFP relies on the menstrual calendar only to distinguish likely fertile from nonfertile days.