Fertility awareness-based methods of family planning help women to identify the days of the cycle they should avoid unprotected intercourse to prevent pregnancy. Therefore using fertility awareness-based methods influences the timing of sexual activity, which may affect the nature of the sexual relationship. Data are used from the clinical trials of two fertility awareness-based methods--the Standard Days Method and the TwoDay Method--to determine the frequency and timing of intercourse during the cycle, and the determinants of coital frequency. The mean coital frequency of study participants was similar to that reported by users of other methods. Results suggest that coital frequency increases with consecutive cycles of method use. At the same time the frequency of intercourse during the identified fertile days and during menses decreases. This evidence implies a behavioural change as couples get more experience using their method and communicating about the fertile days. Coital frequency was also influenced by the method used and by the study sites. Potential differences between the methods and sites that may contribute to this effect are discussed.