Using a sample of 3080 women from Cebu, Philippines, interviewed immediately after childbirth and every 2 months thereafter for 2 years, the determinants of return to coitus are analysed. Eighty percent of the women returned to coitus before the return of menses, and 90% did so before stopping breast-feeding. In hazards models, variables associated with traditional life styles retarded return to coitus. Situational variables (husband resident, crowding, children aged 6 and under), especially husband residence, and biological variables (mother's age, return to menses, and lactation) were significant predictors of return to coitus. The implications of the analysis for the construction of models of birth interval dynamics are discussed.