The Circumcision Impact Study is a series of three household surveys conducted in Kisumu, Kenya, from 2008 to 2013 to assess the impact of the voluntary medical male circumcision (VMMC) programme on knowledge of and attitudes toward the procedure, adoption of male circumcision, sexual risk behavior, and HIV infection rates. The interim results described in this report show that the percentage of men in Kisumu who are circumcised nearly doubled over the first four years of Kenya's VMMC programme, rising from 32 percent in 2008 to 60 percent in 2013, with no associated increases in reported HIV-risk behavior.