Natural family planning includes the calendar (rhythm), basal body temperature, ovulation (mucus), and sympto-thermal methods. Reliability of such methods often is underestimated, but effectiveness of various methods has been reported. Correct understanding and use of proper techniques, primarily abstinence during fertile periods, is imperative for effectiveness. New methods being studied may heighten awareness of fertile times and shorten required periods of abstinence or use of back-up methods.