The FOster Care Expert System (FOCES) was developed to provide advice to social workers of the Roanoke City Department of Social Services who must select foster care homes for children who cannot remain with their own families. It was implemented using the General pUrpose Expert Shell System (GUESS) and Horn Clause Prolog. The system's design was greatly influenced by unique features of the problem domain. Among the key concerns were: unresolved questions within the social work profession about foster home selection and evaluation, serious methodological and philosophical difficulties associated with defining a good "person-environment fit", and the volatile, free-form narrative nature of the information maintained by social services agencies about children and homes. "Traditional" approaches to knowledge acquisition and representation adopted by developers of expert systems were of limited use. Adaptation of extended "p-norm" Boolean queries previously used in information retrieval work simplified the knowledge representation and matching tasks for this human services application. Evaluation of FOCES' performance, using a small database of children and homes, has shown that the system can select appropriate foster care placements at least as well as some experienced social workers.