There has been a resurgence of interest in human ecosystems, attributable to the growth of community mental health centers and public sector funding. The first of two papers discusses human ecology models based on this resurgence. Implications for future development of the mental health area are presented with the challenge to integrate information, activities, and data through the use of a common conceptual framework. The second paper concerns ecotherapy--any clinical approach utilizing the ecological perspective in assessment, diagnosis or intervention. The human ecosystem, the unitary system of interaction between humans and their environment, is divided into structural levels (individual, interpersonal, familial, community, and cultural) and conceptualized in terms of the distribution and dynamic processing of energy or resources. Health in a family is defined as a measure of the ability of individuals to interface with the community. Mediation of needs and resources of individual members and the community is described as a function of the family structure. Implications and techniques for assessment, diagnosis, and intervention are also discussed. (Author/NRB)