Data on infant feeding practices from the 1981 Contraceptive Prevalence Survey permit the updating of a recent study of trends and differentials in breastfeeding in Thailand and provide valuable new information on the extent of full breastfeeding, the type of supplemental foods given infants, and the duration of postpartum amenorrhea. While the results are inconclusive in terms of indicating whether a decline in breastfeeding continued since 1979, the year for which the last national survey provides evidence, they at least confirm the lower levels of breastfeeding found in the 1979 survey in comparison with earlier surveys. The results clearly indicate that breastfeeding mothers introduce supplemental food into the child's diet at a very early age and thus that full breastfeeding is quite short.