"A transitional object" is the first possession that an infant places a special attachment toward, which is not part of him/herself. Typical examples are towels, blankets and teddy bears. The purpose of this study was to investigate the determinants of appearance and disappearance of transitional objects with a special focus on the two factors of "nursing environment" and "marital stress." Two-hundred-and-eleven mothers were asked to complete a questionnaire survey through personal interviews. The main findings were as follows : (1) Transitional objects appeared in bottle-fed infants more often than breast-fed infants ; (2) Infants with younger siblings parted with their transitional objects later than those with older siblings and those without any siblings ; (3) Most transitional objects tended to appear simultaneously with the mothers' stopping breastfeeding ; (4) Transitional objects tended to appear in infants whose mothers had a stressful relationship with their husbands, relative to those who did not. Based on these findings, the "Transitional Object Acquiring Process Model" was presented.