Visitor carrying capacity has been a long-standing issue in management of parks and protected areas. Contemporary carrying capacity frameworks rely on formulation of indicators and standards of quality to define and manage carrying capacity. This paper describes a program of research to support management of carrying capacity of the Boston Harbor Islands national park area, a recent addition to the national park system. Research included: (1) an inventory and analysis of recreation-related resource impacts on selected islands, and (2) surveys of visitors to islands open to public use. Study findings are being incorporated into a visitor carrying capacity management plan through formulation of indicators and standards of quality for the park's natural resources and visitor experience.