Health promotion strategies continue to evolve, with interventions using e-mail, text messaging, and Web sites becoming commonplace. The use of online virtual worlds is a less familiar venue for health promotion but offers numerous possibilities for wired citizens with health issues. The authors discuss three examples of virtual worlds--the River City Project, Whyville, and Second Life--and how health promotion strategies can be implemented in virtual worlds. They also address several challenges associated with implementing health interventions in virtual worlds, including questions of ethics, diffusion of health knowledge and logistics of intervening outside of the real world.