Trust, in much the same way as hope, represents one of the essential components of a healthy upbringing. This article investigates the concept of trust as set forth in Eric Erikson's and Louise Kaplan's theories of basic trust, with particular emphasis on definition and development. The article analyzes some of the criteria that have been presented in describing Reactive Attachment Disorder, insofar as it pertains to the child's not having developed proper attachments to trustworthy individuals and their associated behavior. Finally, the article attempts to correlate foster care placement as one of the main influences leading to mistrust, being more prevalent than trust, and as a resolution of the first stage of psychosocial development, and the rising statistics of Reactive Attachment Disorder. Suggestions for intervention with vulnerable infants are explored, as are implications of using foster care as a context for such intervention. (Contains 23 references.) (Author/HTH)