Promoting male circumcision (MC) is now recognized as an additional, important strategy for the prevention of heterosexually acquired HIV infection in men, and plans are underway to scale-up this intervention especially in non-circumcising communities, with generalized HIV pandemic. This qualitative study identifies and characterizes the role of social and interpersonal factors in the scale-up of MC services in a rural non-circumcising community in western Kenya. Twenty-four sex-specific focus group discussions were conducted with a purposive sample of Luo men and women (15-34 years). Peer and youth groups, girlfriends and women, parents, and cultural political, religious, school leaders were identified as key influences in the scale-up of MC services. The study concludes that social and interpersonal forces create opportunities and constraints for scaling up the MC intervention. Planners of MC projects should therefore harness the power of informal networks and social structures to enhance community engagement, motivate behaviour change and increase demand for MC services