Becoming a mother-in-law is a challenging task but one which has received little serious attention from theorists and researchers. In Family Life Cycle developmental theory, this stage has been referred to as a post-parenting phase. In Family and Couple Developmental Theory, emphasis is placed on the need of the individual or couple to separate from families of origin. In this context, theorists and therapists advise mothers to step back gracefully and to divert their energies elsewhere. An exploratory study was conducted which involved interviews with 24 mothers whose daughters had married not longer than 10 years ago. A significant finding of the study was that the mothers appeared to have an ongoing parenting role during the phase of their daughters' growing relationship with their future husbands, and during the earlier years of marriage. Subjects' descriptions challenge the notion of a non-existent or static role during this phase, and also challenge the emphasis in Developmental Theory on separation and individuation. During the last decade, feminist researchers, clinicians, and scholars have questioned this emphasis in their description of women's development. Surrey (1985) used the construct "relationship differentiation" as a contrast to the idea of separation/individuation. There is a clear congruence between Surrey's concept of developmental relationship differentiation and the description given by the research subjects of their relationships with their adult daughters. (Author/NB)