The authors report on the nature of assessing functional caregiving (FC) via three studies, conducted by a university-public preschool collaboration that was designed to measure mothers' confidence to care for children with intellectual disabilities in their homes. Caregiving of children with intellectual disabilities was conceptualized in terms of a task hierarchy that occurs in a complex, multi-level sociocultural ecology. Rating scale items were developed to survey mothers' caregiving confidence in this ecology, which were analyzed with a Rasch model. Raw ratings were transformed to an axiomatically strong, objective, unidimensional scale, and the obtained task difficulties conformed to a three-tier caregiving hierarchy of advocacy, personal caregiving, and community relations domains. Hierarchical regression of task difficulties on item components defined by FC domains was consistent with an ecological model (R[superscript 2] greater than 0.60). The task hierarchy was also found to be consistent with humanistic psychology principles. When FC measurement properties were compared between suburban and urban mothers, as well as mothers of educationally at risk and special needs children, psychometric reliability was high (greater than 0.90). Validity studies confirmed FC functional relations with mothers' health, age, and economic status. In general, these studies found that mothers' self-confidence measures were valid and reliable, but noted future studies are needed to link FC measures directly to competency and home caregiving quality. Future research should also explore replication of core items across other disabilities and chronic diseases, as well as applicability to objective caregiving standard setting.