AbstractData were provided by 2 surveys on human sexual behavior. Variation of marital coital rate with each of four demographic variables (wife's age, husband's age, parity and social class) was analysed when the other three were held constant. The following results were obtained: 1. When social class and parity (number' of children) are held constant, coital rates decline more rapidly with husband's age than with wife's age. 2. When duration of marriage is held constant, coital rate correlates positively with parity.