This document is a report of a field study on multiple and concurrent sexual partnerships (MCP) in Malawi commissioned by the Research to Prevention (R2P), with funding from the United States Agency for International Development (USAID) and technical assistance from the Johns Hopkins University. The study starts from the premise that multiple concurrent sexual partnerships (MCP), coupled with inconsistent use of condom, has been linked with increased risk of HIV infection. In places where HIV infection has shown significant signs of decline, such as in Uganda, Kenya, Zimbabwe, Zambia and Thailand, evidence strongly suggests that partner reduction has played a crucial role in infection reduction. The diversity and strength of available evidence underscore the need for efforts that promote MCP reduction as a strategy for HIV control. To design and scale up strategies that will effectively promote partner reduction and change the social norms that facilitate MCP, there is need for a strong evidence base concerning the individual predisposing factors and the socio-cultural props of the behavior.