Any estimate of the number of homeless persons involves several definitional issues, including the underlying conceptual definition of homelessness; the intended use of, and rationale for, the count; how the conceptual definition is translated into operational procedures; and methodological choices. These issues are at least partially responsible for the variation in existing estimates of homeless individuals. To best serve multiple constituencies and demands for information, the adoption of a broad definition is recommended. Furthermore, it is necessary to develop and report estimates for specific policy-relevant subgroups of homeless persons, as well as to develop a family of research studies that can yield an understanding of the conditions facing the homeless and identify markers for those who are at risk of becoming homeless (authors).