Data from the Thailand Demographic and Health Survey permit a detailed examination of the pattern of contraceptive initiation in terms both of first post-marital contraceptive use and initiation of use following childbirth. A clear trend towards beginning contraception earlier in the family-building process over the course of the fertility transition is evident. During the earliest stage, contraception was first used mainly after a couple had already achieved their desired family size, but later on couples increasingly began use in order to space births, and most recently it has become common to begin use to delay the start of childbearing. There are two distinctive patterns of contraceptive initiation following childbirth. For women who chose sterilization, initiation occurs during the immediate post partum period, while for those who used other methods, use most commonly began shortly after the return of menses. As a result, few Thai women are at present unprotected against unplanned pregnancies for any substantial period of risk following childbirth. Beginning to use contraception early in the family-building process and rapid adoption of contraception following childbirth are now found in most segments of Thai society, testifying to the maturing of Tailand's fertility transition.